diff options
| -rw-r--r-- | Documentation/filesystems/devfs/ChangeLog | 1977 | ||||
| -rw-r--r-- | Documentation/filesystems/devfs/README | 1959 | ||||
| -rw-r--r-- | Documentation/filesystems/devfs/ToDo | 40 | ||||
| -rw-r--r-- | Documentation/filesystems/devfs/boot-options | 65 |
4 files changed, 0 insertions, 4041 deletions
diff --git a/Documentation/filesystems/devfs/ChangeLog b/Documentation/filesystems/devfs/ChangeLog deleted file mode 100644 index e5aba52..0000000 --- a/Documentation/filesystems/devfs/ChangeLog +++ /dev/null @@ -1,1977 +0,0 @@ -/* -*- auto-fill -*- */ -=============================================================================== -Changes for patch v1 - -- creation of devfs - -- modified miscellaneous character devices to support devfs -=============================================================================== -Changes for patch v2 - -- bug fix with manual inode creation -=============================================================================== -Changes for patch v3 - -- bugfixes - -- documentation improvements - -- created a couple of scripts (one to save&restore a devfs and the - other to set up compatibility symlinks) - -- devfs support for SCSI discs. New name format is: sd_hHcCiIlL -=============================================================================== -Changes for patch v4 - -- bugfix for the directory reading code - -- bugfix for compilation with kerneld - -- devfs support for generic hard discs - -- rationalisation of the various watchdog drivers -=============================================================================== -Changes for patch v5 - -- support for mounting directly from entries in the devfs (it doesn't - need to be mounted to do this), including the root filesystem. - Mounting of swap partitions also works. Hence, now if you set - CONFIG_DEVFS_ONLY to 'Y' then you won't be able to access your discs - via ordinary device nodes. Naturally, the default is 'N' so that you - can still use your old device nodes. If you want to mount from devfs - entries, make sure you use: append = "root=/dev/sd_..." in your - lilo.conf. It seems LILO looks for the device number (major&minor) - and writes that into the kernel image :-( - -- support for character memory devices (/dev/null, /dev/zero, /dev/full - and so on). Thanks to C. Scott Ananian <cananian@alumni.princeton.edu> -=============================================================================== -Changes for patch v6 - -- support for subdirectories - -- support for symbolic links (created by devfs_mk_symlink(), no - support yet for creation via symlink(2)) - -- SCSI disc naming now cast in stone, with the format: - /dev/sd/c0b1t2u3 controller=0, bus=1, ID=2, LUN=3, whole disc - /dev/sd/c0b1t2u3p4 controller=0, bus=1, ID=2, LUN=3, 4th partition - -- loop devices now appear in devfs - -- tty devices, console, serial ports, etc. now appear in devfs - Thanks to C. Scott Ananian <cananian@alumni.princeton.edu> - -- bugs with mounting devfs-only devices now fixed -=============================================================================== -Changes for patch v7 - -- SCSI CD-ROMS, tapes and generic devices now appear in devfs -=============================================================================== -Changes for patch v8 - -- bugfix with no-rewind SCSI tapes - -- RAMDISCs now appear in devfs - -- better cleaning up of devfs entries created by various modules - -- interface change to <devfs_register> -=============================================================================== -Changes for patch v9 - -- the v8 patch was corrupted somehow, which would affect the patch for - linux/fs/filesystems.c - I've also fixed the v8 patch file on the WWW - -- MetaDevices (/dev/md*) should now appear in devfs -=============================================================================== -Changes for patch v10 - -- bugfix in meta device support for devfs - -- created this ChangeLog file - -- added devfs support to the floppy driver - -- added support for creating sockets in a devfs -=============================================================================== -Changes for patch v11 - -- added DEVFS_FL_HIDE_UNREG flag - -- incorporated better patch for ttyname() in libc 5.4.43 from H.J. Lu. - -- interface change to <devfs_mk_symlink> - -- support for creating symlinks with symlink(2) - -- parallel port printer (/dev/lp*) now appears in devfs -=============================================================================== -Changes for patch v12 - -- added inode check to <devfs_fill_file> function - -- improved devfs support when mounting from devfs - -- added call to <<release>> operation when removing swap areas on - devfs devices - -- increased NR_SUPER to 128 to support large numbers of devfs mounts - (for chroot(2) gaols) - -- fixed bug in SCSI disc support: was generating incorrect minors if - SCSI ID's did not start at 0 and increase by 1 - -- support symlink traversal when mounting root -=============================================================================== -Changes for patch v13 - -- added devfs support to soundcard driver - Thanks to Eric Dumas <dumas@linux.eu.org> and - C. Scott Ananian <cananian@alumni.princeton.edu> - -- added devfs support to the joystick driver - -- loop driver now has it's own subdirectory "/dev/loop/" - -- created <devfs_get_flags> and <devfs_set_flags> functions - -- fix problem with SCSI disc compatibility names (sd{a,b,c,d,e,f}) - which assumes ID's start at 0 and increase by 1. Also only create - devfs entries for SCSI disc partitions which actually exist - Show new names in partition check - Thanks to Jakub Jelinek <jj@sunsite.ms.mff.cuni.cz> -=============================================================================== -Changes for patch v14 - -- bug fix in floppy driver: would not compile without - CONFIG_DEVFS_FS='Y' - Thanks to Jurgen Botz <jbotz@nova.botz.org> - -- bug fix in loop driver - Thanks to C. Scott Ananian <cananian@alumni.princeton.edu> - -- do not create devfs entries for printers not configured - Thanks to C. Scott Ananian <cananian@alumni.princeton.edu> - -- do not create devfs entries for serial ports not present - Thanks to C. Scott Ananian <cananian@alumni.princeton.edu> - -- ensure <tty_register_devfs> is exported from tty_io.c - Thanks to C. Scott Ananian <cananian@alumni.princeton.edu> - -- allow unregistering of devfs symlink entries - -- fixed bug in SCSI disc naming introduced in last patch version -=============================================================================== -Changes for patch v15 - -- ported to kernel 2.1.81 -=============================================================================== -Changes for patch v16 - -- created <devfs_set_symlink_destination> function - -- moved DEVFS_SUPER_MAGIC into header file - -- added DEVFS_FL_HIDE flag - -- created <devfs_get_maj_min> - -- created <devfs_get_handle_from_inode> - -- fixed bugs in searching by major&minor - -- changed interface to <devfs_unregister>, <devfs_fill_file> and - <devfs_find_handle> - -- fixed inode times when symlink created with symlink(2) - -- change tty driver to do auto-creation of devfs entries - Thanks to C. Scott Ananian <cananian@alumni.princeton.edu> - -- fixed bug in genhd.c: whole disc (non-SCSI) was not registered to - devfs - -- updated libc 5.4.43 patch for ttyname() -=============================================================================== -Changes for patch v17 - -- added CONFIG_DEVFS_TTY_COMPAT - Thanks to C. Scott Ananian <cananian@alumni.princeton.edu> - -- bugfix in devfs support for drivers/char/lp.c - Thanks to C. Scott Ananian <cananian@alumni.princeton.edu> - -- clean up serial driver so that PCMCIA devices unregister correctly - Thanks to C. Scott Ananian <cananian@alumni.princeton.edu> - -- fixed bug in genhd.c: whole disc (non-SCSI) was not registered to - devfs [was missing in patch v16] - -- updated libc 5.4.43 patch for ttyname() [was missing in patch v16] - -- all SCSI devices now registered in /dev/sg - -- support removal of devfs entries via unlink(2) -=============================================================================== -Changes for patch v18 - -- added floppy/?u720 floppy entry - -- fixed kerneld support for entries in devfs subdirectories - -- incorporated latest patch for ttyname() in libc 5.4.43 from H.J. Lu. -=============================================================================== -Changes for patch v19 - -- bug fix when looking up unregistered entries: kerneld was not called - -- fixes for kernel 2.1.86 (now requires 2.1.86) -=============================================================================== -Changes for patch v20 - -- only create available floppy entries - Thanks to Andrzej Krzysztofowicz <ankry@green.mif.pg.gda.pl> - -- new IDE naming scheme following SCSI format (i.e. /dev/id/c0b0t0u0p1 - instead of /dev/hda1) - Thanks to Andrzej Krzysztofowicz <ankry@green.mif.pg.gda.pl> - -- new XT disc naming scheme following SCSI format (i.e. /dev/xd/c0t0p1 - instead of /dev/xda1) - Thanks to Andrzej Krzysztofowicz <ankry@green.mif.pg.gda.pl> - -- new non-standard CD-ROM names (i.e. /dev/sbp/c#t#) - Thanks to Andrzej Krzysztofowicz <ankry@green.mif.pg.gda.pl> - -- allow symlink traversal when mounting the root filesystem - -- Create entries for MD devices at MD init - Thanks to Christophe Leroy <christophe.leroy5@capway.com> -=============================================================================== -Changes for patch v21 - -- ported to kernel 2.1.91 -=============================================================================== -Changes for patch v22 - -- SCSI host number patch ("scsihosts=" kernel option) - Thanks to Andrzej Krzysztofowicz <ankry@green.mif.pg.gda.pl> -=============================================================================== -Changes for patch v23 - -- Fixed persistence bug with device numbers for manually created - device files - -- Fixed problem with recreating symlinks with different content - -- Added CONFIG_DEVFS_MOUNT (mount devfs on /dev at boot time) -=============================================================================== -Changes for patch v24 - -- Switched from CONFIG_KERNELD to CONFIG_KMOD: module autoloading - should now work again - -- Hide entries which are manually unlinked - -- Always invalidate devfs dentry cache when registering entries - -- Support removal of devfs directories via rmdir(2) - -- Ensure directories created by <devfs_mk_dir> are visible - -- Default no access for "other" for floppy device -=============================================================================== -Changes for patch v25 - -- Updates to CREDITS file and minor IDE numbering change - Thanks to Andrzej Krzysztofowicz <ankry@green.mif.pg.gda.pl> - -- Invalidate devfs dentry cache when making directories - -- Invalidate devfs dentry cache when removing entries - -- More informative message if root FS mount fails when devfs - configured - -- Fixed persistence bug with fifos -=============================================================================== -Changes for patch v26 - -- ported to kernel 2.1.97 - -- Changed serial directory from "/dev/serial" to "/dev/tts" and - "/dev/consoles" to "/dev/vc" to be more friendly to new procps -=============================================================================== -Changes for patch v27 - -- Added support for IDE4 and IDE5 - Thanks to Andrzej Krzysztofowicz <ankry@green.mif.pg.gda.pl> - -- Documented "scsihosts=" boot parameter - -- Print process command when debugging kerneld/kmod - -- Added debugging for register/unregister/change operations - -- Added "devfs=" boot options - -- Hide unregistered entries by default -=============================================================================== -Changes for patch v28 - -- No longer lock/unlock superblock in <devfs_put_super> (cope with - recent VFS interface change) - -- Do not automatically change ownership/protection of /dev/tty - -- Drop negative dentries when they are released - -- Manage dcache more efficiently -=============================================================================== -Changes for patch v29 - -- Added DEVFS_FL_AUTO_DEVNUM flag -=============================================================================== -Changes for patch v30 - -- No longer set unnecessary methods - -- Ported to kernel 2.1.99-pre3 -=============================================================================== -Changes for patch v31 - -- Added PID display to <call_kerneld> debugging message - -- Added "diread" and "diwrite" options - -- Ported to kernel 2.1.102 - -- Fixed persistence problem with permissions -=============================================================================== -Changes for patch v32 - -- Fixed devfs support in drivers/block/md.c -=============================================================================== -Changes for patch v33 - -- Support legacy device nodes - -- Fixed bug where recreated inodes were hidden - -- New IDE naming scheme: everything is under /dev/ide -=============================================================================== -Changes for patch v34 - -- Improved debugging in <get_vfs_inode> - -- Prevent duplicate calls to <devfs_mk_dir> in SCSI layer - -- No longer free old dentries in <devfs_mk_dir> - -- Free all dentries for a given entry when deleting inodes -=============================================================================== -Changes for patch v35 - -- Ported to kernel 2.1.105 (sound driver changes) -=============================================================================== -Changes for patch v36 - -- Fixed sound driver port -=============================================================================== -Changes for patch v37 - -- Minor documentation tweaks -=============================================================================== -Changes for patch v38 - -- More documentation tweaks - -- Fix for sound driver port - -- Removed ttyname-patch (grab libc 5.4.44 instead) - -- Ported to kernel 2.1.107-pre2 (loop driver fix) -=============================================================================== -Changes for patch v39 - -- Ported to kernel 2.1.107 (hd.c hunk broke due to spelling "fixes"). Sigh - -- Removed many #ifdef's, replaced with trickery in include/devfs_fs.h -=============================================================================== -Changes for patch v40 - -- Fix for sound driver port - -- Limit auto-device numbering to majors 128 to 239 -=============================================================================== -Changes for patch v41 - -- Fixed inode times persistence problem -=============================================================================== -Changes for patch v42 - -- Ported to kernel 2.1.108 (drivers/scsi/hosts.c hunk broke) -=============================================================================== -Changes for patch v43 - -- Fixed spelling in <devfs_readlink> debug - -- Fixed bug in <devfs_setup> parsing "dilookup" - -- More #ifdef's removed - -- Supported Sparc keyboard (/dev/kbd) - -- Supported DSP56001 digital signal processor (/dev/dsp56k) - -- Supported Apple Desktop Bus (/dev/adb) - -- Supported Coda network file system (/dev/cfs*) -=============================================================================== -Changes for patch v44 - -- Fixed devfs inode leak when manually recreating inodes - -- Fixed permission persistence problem when recreating inodes -=============================================================================== -Changes for patch v45 - -- Ported to kernel 2.1.110 -=============================================================================== -Changes for patch v46 - -- Ported to kernel 2.1.112-pre1 - -- Removed harmless "unused variable" compiler warning - -- Fixed modes for manually recreated device nodes -=============================================================================== -Changes for patch v47 - -- Added NULL devfs inode warning in <devfs_read_inode> - -- Force all inode nlink values to 1 -=============================================================================== -Changes for patch v48 - -- Added "dimknod" option - -- Set inode nlink to 0 when freeing dentries - -- Added support for virtual console capture devices (/dev/vcs*) - Thanks to Dennis Hou <smilax@mindmeld.yi.org> - -- Fixed modes for manually recreated symlinks -=============================================================================== -Changes for patch v49 - -- Ported to kernel 2.1.113 -=============================================================================== -Changes for patch v50 - -- Fixed bugs in recreated directories and symlinks -=============================================================================== -Changes for patch v51 - -- Improved robustness of rc.devfs script - Thanks to Roderich Schupp <rsch@experteam.de> - -- Fixed bugs in recreated device nodes - -- Fixed bug in currently unused <devfs_get_handle_from_inode> - -- Defined new <devfs_handle_t> type - -- Improved debugging when getting entries - -- Fixed bug where directories could be emptied - -- Ported to kernel 2.1.115 -=============================================================================== -Changes for patch v52 - -- Replaced dummy .epoch inode with .devfsd character device - -- Modified rc.devfs to take account of above change - -- Removed spurious driver warning messages when CONFIG_DEVFS_FS=n - -- Implemented devfsd protocol revision 0 -=============================================================================== -Changes for patch v53 - -- Ported to kernel 2.1.116 (kmod change broke hunk) - -- Updated Documentation/Configure.help - -- Test and tty pattern patch for rc.devfs script - Thanks to Roderich Schupp <rsch@experteam.de> - -- Added soothing message to warning in <devfs_d_iput> -=============================================================================== -Changes for patch v54 - -- Ported to kernel 2.1.117 - -- Fixed default permissions in sound driver - -- Added support for frame buffer devices (/dev/fb*) -=============================================================================== -Changes for patch v55 - -- Ported to kernel 2.1.119 - -- Use GCC extensions for structure initialisations - -- Implemented async open notification - -- Incremented devfsd protocol revision to 1 -=============================================================================== -Changes for patch v56 - -- Ported to kernel 2.1.120-pre3 - -- Moved async open notification to end of <devfs_open> -=============================================================================== -Changes for patch v57 - -- Ported to kernel 2.1.121 - -- Prepended "/dev/" to module load request - -- Renamed <call_kerneld> to <call_kmod> - -- Created sample modules.conf file -=============================================================================== -Changes for patch v58 - -- Fixed typo "AYSNC" -> "ASYNC" -=============================================================================== -Changes for patch v59 - -- Added open flag for files -=============================================================================== -Changes for patch v60 - -- Ported to kernel 2.1.123-pre2 -=============================================================================== -Changes for patch v61 - -- Set i_blocks=0 and i_blksize=1024 in <devfs_read_inode> -=============================================================================== -Changes for patch v62 - -- Ported to kernel 2.1.123 -=============================================================================== -Changes for patch v63 - -- Ported to kernel 2.1.124-pre2 -=============================================================================== -Changes for patch v64 - -- Fixed Unix98 pty support - -- Increased buffer size in <get_partition_list> to avoid crash and - burn -=============================================================================== -Changes for patch v65 - -- More Unix98 pty support fixes - -- Added test for empty <<name>> in <devfs_find_handle> - -- Renamed <generate_path> to <devfs_generate_path> and published - -- Created /dev/root symlink - Thanks to Roderich Schupp <rsch@ExperTeam.de> - with further modifications by me -=============================================================================== -Changes for patch v66 - -- Yet more Unix98 pty support fixes (now tested) - -- Created <devfs_get_fops> - -- Support media change checks when CONFIG_DEVFS_ONLY=y - -- Abolished Unix98-style PTY names for old PTY devices -=============================================================================== -Changes for patch v67 - -- Added inline declaration for dummy <devfs_generate_path> - -- Removed spurious "unable to register... in devfs" messages when - CONFIG_DEVFS_FS=n - -- Fixed misc. devices when CONFIG_DEVFS_FS=n - -- Limit auto-device numbering to majors 144 to 239 -=============================================================================== -Changes for patch v68 - -- Hide unopened virtual consoles from directory listings - -- Added support for video capture devices - -- Ported to kernel 2.1.125 -=============================================================================== -Changes for patch v69 - -- Fix for CONFIG_VT=n -=============================================================================== -Changes for patch v70 - -- Added support for non-OSS/Free sound cards -=============================================================================== -Changes for patch v71 - -- Ported to kernel 2.1.126-pre2 -=============================================================================== -Changes for patch v72 - -- #ifdef's for CONFIG_DEVFS_DISABLE_OLD_NAMES removed -=============================================================================== -Changes for patch v73 - -- CONFIG_DEVFS_DISABLE_OLD_NAMES replaced with "nocompat" boot option - -- CONFIG_DEVFS_BOOT_OPTIONS removed: boot options always available -=============================================================================== -Changes for patch v74 - -- Removed CONFIG_DEVFS_MOUNT and "mount" boot option and replaced with - "nomount" boot option - -- Documentation updates - -- Updated sample modules.conf -=============================================================================== -Changes for patch v75 - -- Updated sample modules.conf - -- Remount devfs after initrd finishes - -- Ported to kernel 2.1.127 - -- Added support for ISDN - Thanks to Christophe Leroy <christophe.leroy5@capway.com> -=============================================================================== -Changes for patch v76 - -- Updated an email address in ChangeLog - -- CONFIG_DEVFS_ONLY replaced with "only" boot option -=============================================================================== -Changes for patch v77 - -- Added DEVFS_FL_REMOVABLE flag - -- Check for disc change when listing directories with removable media - devices - -- Use DEVFS_FL_REMOVABLE in sd.c - -- Ported to kernel 2.1.128 -=============================================================================== -Changes for patch v78 - -- Only call <scan_dir_for_removable> on first call to <devfs_readdir> - -- Ported to kernel 2.1.129-pre5 - -- ISDN support improvements - Thanks to Christophe Leroy <christophe.leroy5@capway.com> -=============================================================================== -Changes for patch v79 - -- Ported to kernel 2.1.130 - -- Renamed miscdevice "apm" to "apm_bios" to be consistent with - devices.txt -=============================================================================== -Changes for patch v80 - -- Ported to kernel 2.1.131 - -- Updated <devfs_rmdir> for VFS change in 2.1.131 -=============================================================================== -Changes for patch v81 - -- Fixed permissions on /dev/ptmx -=============================================================================== -Changes for patch v82 - -- Ported to kernel 2.1.132-pre4 - -- Changed initial permissions on /dev/pts/* - -- Created <devfs_mk_compat> - -- Added "symlinks" boot option - -- Changed devfs_register_blkdev() back to register_blkdev() for IDE - -- Check for partitions on removable media in <devfs_lookup> -=============================================================================== -Changes for patch v83 - -- Fixed support for ramdisc when using string-based root FS name - -- Ported to kernel 2.2.0-pre1 -=============================================================================== -Changes for patch v84 - -- Ported to kernel 2.2.0-pre7 -=============================================================================== -Changes for patch v85 - -- Compile fixes for driver/sound/sound_common.c (non-module) and - drivers/isdn/isdn_common.c - Thanks to Christophe Leroy <christophe.leroy5@capway.com> - -- Added support for registering regular files - -- Created <devfs_set_file_size> - -- Added /dev/cpu/mtrr as an alternative interface to /proc/mtrr - -- Update devfs inodes from entries if not changed through FS -=============================================================================== -Changes for patch v86 - -- Ported to kernel 2.2.0-pre9 -=============================================================================== -Changes for patch v87 - -- Fixed bug when mounting non-devfs devices in a devfs -=============================================================================== -Changes for patch v88 - -- Fixed <devfs_fill_file> to only initialise temporary inodes - -- Trap for NULL fops in <devfs_register> - -- Return -ENODEV in <devfs_fill_file> for non-driver inodes - -- Fixed bug when unswapping non-devfs devices in a devfs -=============================================================================== -Changes for patch v89 - -- Switched to C data types in include/linux/devfs_fs.h - -- Switched from PATH_MAX to DEVFS_PATHLEN - -- Updated Documentation/filesystems/devfs/modules.conf to take account - of reverse scanning (!) by modprobe - -- Ported to kernel 2.2.0 -=============================================================================== -Changes for patch v90 - -- CONFIG_DEVFS_DISABLE_OLD_TTY_NAMES replaced with "nottycompat" boot - option - -- CONFIG_DEVFS_TTY_COMPAT removed: existing "symlinks" boot option now - controls this. This means you must have libc 5.4.44 or later, or a - recent version of libc 6 if you use the "symlinks" option -=============================================================================== -Changes for patch v91 - -- Switch from <devfs_mk_symlink> to <devfs_mk_compat> in - drivers/char/vc_screen.c to fix problems with Midnight Commander -=============================================================================== -Changes for patch v92 - -- Ported to kernel 2.2.2-pre5 -=============================================================================== -Changes for patch v93 - -- Modified <sd_name> in drivers/scsi/sd.c to cope with devices that - don't exist (which happens with new RAID autostart code printk()s) -=============================================================================== -Changes for patch v94 - -- Fixed bug in joystick driver: only first joystick was registered -=============================================================================== -Changes for patch v95 - -- Fixed another bug in joystick driver - -- Fixed <devfsd_read> to not overrun event buffer -=============================================================================== -Changes for patch v96 - -- Ported to kernel 2.2.5-2 - -- Created <devfs_auto_unregister> - -- Fixed bugs: compatibility entries were not unregistered for: - loop driver - floppy driver - RAMDISC driver - IDE tape driver - SCSI CD-ROM driver - SCSI HDD driver -=============================================================================== -Changes for patch v97 - -- Fixed bugs: compatibility entries were not unregistered for: - ALSA sound driver - partitions in generic disc driver - -- Don't return unregistred entries in <devfs_find_handle> - -- Panic in <devfs_unregister> if entry unregistered - -- Don't panic in <devfs_auto_unregister> for duplicates -=============================================================================== -Changes for patch v98 - -- Don't unregister already unregistered entries in <unregister> - -- Register entry in <sd_detect> - -- Unregister entry in <sd_detach> - -- Changed to <devfs_*register_chrdev> in drivers/char/tty_io.c - -- Ported to kernel 2.2.7 -=============================================================================== -Changes for patch v99 - -- Ported to kernel 2.2.8 - -- Fixed bug in drivers/scsi/sd.c when >16 SCSI discs - -- Disable warning messages when unable to read partition table for - removable media -=============================================================================== -Changes for patch v100 - -- Ported to kernel 2.3.1-pre5 - -- Added "oops-on-panic" boot option - -- Improved debugging in <devfs_register> and <devfs_unregister> - -- Register entry in <sr_detect> - -- Unregister entry in <sr_detach> - -- Register entry in <sg_detect> - -- Unregister entry in <sg_detach> - -- Added support for ALSA drivers -=============================================================================== -Changes for patch v101 - -- Ported to kernel 2.3.2 -=============================================================================== -Changes for patch v102 - -- Update serial driver to register PCMCIA entries - Thanks to Roch-Alexandre Nomine-Beguin <roch@samarkand.infini.fr> - -- Updated an email address in ChangeLog - -- Hide virtual console capture entries from directory listings when - corresponding console device is not open -=============================================================================== -Changes for patch v103 - -- Ported to kernel 2.3.3 -=============================================================================== -Changes for patch v104 - -- Added documentation for some functions - -- Added "doc" target to fs/devfs/Makefile - -- Added "v4l" directory for video4linux devices - -- Replaced call to <devfs_unregister> in <sd_detach> with call to - <devfs_register_partitions> - -- Moved registration for sr and sg drivers from detect() to attach() - methods - -- Register entries in <st_attach> and unregister in <st_detach> - -- Work around IDE driver treating CD-ROM as gendisk - -- Use <sed> instead of <tr> in rc.devfs - -- Updated ToDo list - -- Removed "oops-on-panic" boot option: now always Oops -=============================================================================== -Changes for patch v105 - -- Unregister SCSI host from <scsi_host_no_list> in <scsi_unregister> - Thanks to Zoltán Böszörményi <zboszor@mail.externet.hu> - -- Don't save /dev/log in rc.devfs - -- Ported to kernel 2.3.4-pre1 -=============================================================================== -Changes for patch v106 - -- Fixed silly typo in drivers/scsi/st.c - -- Improved debugging in <devfs_register> -=============================================================================== -Changes for patch v107 - -- Added "diunlink" and "nokmod" boot options - -- Removed superfluous warning message in <devfs_d_iput> -=============================================================================== -Changes for patch v108 - -- Remove entries when unloading sound module -=============================================================================== -Changes for patch v109 - -- Ported to kernel 2.3.6-pre2 -=============================================================================== -Changes for patch v110 - -- Took account of change to <d_alloc_root> -=============================================================================== -Changes for patch v111 - -- Created separate event queue for each mounted devfs - -- Removed <devfs_invalidate_dcache> - -- Created new ioctl()s for devfsd - -- Incremented devfsd protocol revision to 3 - -- Fixed bug when re-creating directories: contents were lost - -- Block access to inodes until devfsd updates permissions -=============================================================================== -Changes for patch v112 - -- Modified patch so it applies against 2.3.5 and 2.3.6 - -- Updated an email address in ChangeLog - -- Do not automatically change ownership/protection of /dev/tty<n> - -- Updated sample modules.conf - -- Switched to sending process uid/gid to devfsd - -- Renamed <call_kmod> to <try_modload> - -- Added DEVFSD_NOTIFY_LOOKUP event - -- Added DEVFSD_NOTIFY_CHANGE event - -- Added DEVFSD_NOTIFY_CREATE event - -- Incremented devfsd protocol revision to 4 - -- Moved kernel-specific stuff to include/linux/devfs_fs_kernel.h -=============================================================================== -Changes for patch v113 - -- Ported to kernel 2.3.9 - -- Restricted permissions on some block devices -=============================================================================== -Changes for patch v114 - -- Added support for /dev/netlink - Thanks to Dennis Hou <smilax@mindmeld.yi.org> - -- Return EISDIR rather than EINVAL for read(2) on directories - -- Ported to kernel 2.3.10 -=============================================================================== -Changes for patch v115 - -- Added support for all remaining character devices - Thanks to Dennis Hou <smilax@mindmeld.yi.org> - -- Cleaned up netlink support -=============================================================================== -Changes for patch v116 - -- Added support for /dev/parport%d - Thanks to Tim Waugh <tim@cyberelk.demon.co.uk> - -- Fixed parallel port ATAPI tape driver - -- Fixed Atari SLM laser printer driver -=============================================================================== -Changes for patch v117 - -- Added support for COSA card - Thanks to Dennis Hou <smilax@mindmeld.yi.org> - -- Fixed drivers/char/ppdev.c: missing #include <linux/init.h> - -- Fixed drivers/char/ftape/zftape/zftape-init.c - Thanks to Vladimir Popov <mashgrad@usa.net> -=============================================================================== -Changes for patch v118 - -- Ported to kernel 2.3.15-pre3 - -- Fixed bug in loop driver - -- Unregister /dev/lp%d entries in drivers/char/lp.c - Thanks to Maciej W. Rozycki <macro@ds2.pg.gda.pl> -=============================================================================== -Changes for patch v119 - -- Ported to kernel 2.3.16 -=============================================================================== -Changes for patch v120 - -- Fixed bug in drivers/scsi/scsi.c - -- Added /dev/ppp - Thanks to Dennis Hou <smilax@mindmeld.yi.org> - -- Ported to kernel 2.3.17 -=============================================================================== -Changes for patch v121 - -- Fixed bug in drivers/block/loop.c - -- Ported to kernel 2.3.18 -=============================================================================== -Changes for patch v122 - -- Ported to kernel 2.3.19 -=============================================================================== -Changes for patch v123 - -- Ported to kernel 2.3.20 -=============================================================================== -Changes for patch v124 - -- Ported to kernel 2.3.21 -=============================================================================== -Changes for patch v125 - -- Created <devfs_get_info>, <devfs_set_info>, - <devfs_get_first_child> and <devfs_get_next_sibling> - Added <<dir>> parameter to <devfs_register>, <devfs_mk_compat>, - <devfs_mk_dir> and <devfs_find_handle> - Work sponsored by SGI - -- Fixed apparent bug in COSA driver - -- Re-instated "scsihosts=" boot option -=============================================================================== -Changes for patch v126 - -- Always create /dev/pts if CONFIG_UNIX98_PTYS=y - -- Fixed call to <devfs_mk_dir> in drivers/block/ide-disk.c - Thanks to Dennis Hou <smilax@mindmeld.yi.org> - -- Allow multiple unregistrations - -- Created /dev/scsi hierarchy - Work sponsored by SGI -=============================================================================== -Changes for patch v127 - -Work sponsored by SGI - -- No longer disable devpts if devfs enabled (caveat emptor) - -- Added flags array to struct gendisk and removed code from - drivers/scsi/sd.c - -- Created /dev/discs hierarchy -=============================================================================== -Changes for patch v128 - -Work sponsored by SGI - -- Created /dev/cdroms hierarchy -=============================================================================== -Changes for patch v129 - -Work sponsored by SGI - -- Removed compatibility entries for sound devices - -- Removed compatibility entries for printer devices - -- Removed compatibility entries for video4linux devices - -- Removed compatibility entries for parallel port devices - -- Removed compatibility entries for frame buffer devices -=============================================================================== -Changes for patch v130 - -Work sponsored by SGI - -- Added major and minor number to devfsd protocol - -- Incremented devfsd protocol revision to 5 - -- Removed compatibility entries for SoundBlaster CD-ROMs - -- Removed compatibility entries for netlink devices - -- Removed compatibility entries for SCSI generic devices - -- Removed compatibility entries for SCSI tape devices -=============================================================================== -Changes for patch v131 - -Work sponsored by SGI - -- Support info pointer for all devfs entry types - -- Added <<info>> parameter to <devfs_mk_dir> and <devfs_mk_symlink> - -- Removed /dev/st hierarchy - -- Removed /dev/sg hierarchy - -- Removed compatibility entries for loop devices - -- Removed compatibility entries for IDE tape devices - -- Removed compatibility entries for SCSI CD-ROMs - -- Removed /dev/sr hierarchy -=============================================================================== -Changes for patch v132 - -Work sponsored by SGI - -- Removed compatibility entries for floppy devices - -- Removed compatibility entries for RAMDISCs - -- Removed compatibility entries for meta-devices - -- Removed compatibility entries for SCSI discs - -- Created <devfs_make_root> - -- Removed /dev/sd hierarchy - -- Support "../" when searching devfs namespace - -- Created /dev/ide/host* hierarchy - -- Supported IDE hard discs in /dev/ide/host* hierarchy - -- Removed compatibility entries for IDE discs - -- Removed /dev/ide/hd hierarchy - -- Supported IDE CD-ROMs in /dev/ide/host* hierarchy - -- Removed compatibility entries for IDE CD-ROMs - -- Removed /dev/ide/cd hierarchy -=============================================================================== -Changes for patch v133 - -Work sponsored by SGI - -- Created <devfs_get_unregister_slave> - -- Fixed bug in fs/partitions/check.c when rescanning -=============================================================================== -Changes for patch v134 - -Work sponsored by SGI - -- Removed /dev/sd, /dev/sr, /dev/st and /dev/sg directories - -- Removed /dev/ide/hd directory - -- Exported <devfs_get_parent> - -- Created <devfs_register_tape> and /dev/tapes hierarchy - -- Removed /dev/ide/mt hierarchy - -- Removed /dev/ide/fd hierarchy - -- Ported to kernel 2.3.25 -=============================================================================== -Changes for patch v135 - -Work sponsored by SGI - -- Removed compatibility entries for virtual console capture devices - -- Removed unused <devfs_set_symlink_destination> - -- Removed compatibility entries for serial devices - -- Removed compatibility entries for console devices - -- Do not hide entries from devfsd or children - -- Removed DEVFS_FL_TTY_COMPAT flag - -- Removed "nottycompat" boot option - -- Removed <devfs_mk_compat> -=============================================================================== -Changes for patch v136 - -Work sponsored by SGI - -- Moved BSD pty devices to /dev/pty - -- Added DEVFS_FL_WAIT flag -=============================================================================== -Changes for patch v137 - -Work sponsored by SGI - -- Really fixed bug in fs/partitions/check.c when rescanning - -- Support new "disc" naming scheme in <get_removable_partition> - -- Allow NULL fops in <devfs_register> - -- Removed redundant name functions in SCSI disc and IDE drivers -=============================================================================== -Changes for patch v138 - -Work sponsored by SGI - -- Fixed old bugs in drivers/block/paride/pt.c, drivers/char/tpqic02.c, - drivers/net/wan/cosa.c and drivers/scsi/scsi.c - Thanks to Sergey Kubushin <ksi@ksi-linux.com> - -- Fall back to major table if NULL fops given to <devfs_register> -=============================================================================== -Changes for patch v139 - -Work sponsored by SGI - -- Corrected and moved <get_blkfops> and <get_chrfops> declarations - from arch/alpha/kernel/osf_sys.c to include/linux/fs.h - -- Removed name function from struct gendisk - -- Updated devfs FAQ -=============================================================================== -Changes for patch v140 - -Work sponsored by SGI - -- Ported to kernel 2.3.27 -=============================================================================== -Changes for patch v141 - -Work sponsored by SGI - -- Bug fix in arch/m68k/atari/joystick.c - -- Moved ISDN and capi devices to /dev/isdn -=============================================================================== -Changes for patch v142 - -Work sponsored by SGI - -- Bug fix in drivers/block/ide-probe.c (patch confusion) -=============================================================================== -Changes for patch v143 - -Work sponsored by SGI - -- Bug fix in drivers/block/blkpg.c:partition_name() -=============================================================================== -Changes for patch v144 - -Work sponsored by SGI - -- Ported to kernel 2.3.29 - -- Removed calls to <devfs_register> from cdu31a, cm206, mcd and mcdx - CD-ROM drivers: generic driver handles this now - -- Moved joystick devices to /dev/joysticks -=============================================================================== -Changes for patch v145 - -Work sponsored by SGI - -- Ported to kernel 2.3.30-pre3 - -- Register whole-disc entry even for invalid partition tables - -- Fixed bug in mounting root FS when initrd enabled - -- Fixed device entry leak with IDE CD-ROMs - -- Fixed compile problem with drivers/isdn/isdn_common.c - -- Moved COSA devices to /dev/cosa - -- Support fifos when unregistering - -- Created <devfs_register_series> and used in many drivers - -- Moved Coda devices to /dev/coda - -- Moved parallel port IDE tapes to /dev/pt - -- Moved parallel port IDE generic devices to /dev/pg -=============================================================================== -Changes for patch v146 - -Work sponsored by SGI - -- Removed obsolete DEVFS_FL_COMPAT and DEVFS_FL_TOLERANT flags - -- Fixed compile problem with fs/coda/psdev.c - -- Reinstate change to <devfs_register_blkdev> in - drivers/block/ide-probe.c now that fs/isofs/inode.c is fixed - -- Switched to <devfs_register_blkdev> in drivers/block/floppy.c, - drivers/scsi/sr.c and drivers/block/md.c - -- Moved DAC960 devices to /dev/dac960 -=============================================================================== -Changes for patch v147 - -Work sponsored by SGI - -- Ported to kernel 2.3.32-pre4 -=============================================================================== -Changes for patch v148 - -Work sponsored by SGI - -- Removed kmod support: use devfsd instead - -- Moved miscellaneous character devices to /dev/misc -=============================================================================== -Changes for patch v149 - -Work sponsored by SGI - -- Ensure include/linux/joystick.h is OK for user-space - -- Improved debugging in <get_vfs_inode> - -- Ensure dentries created by devfsd will be cleaned up -=============================================================================== -Changes for patch v150 - -Work sponsored by SGI - -- Ported to kernel 2.3.34 -=============================================================================== -Changes for patch v151 - -Work sponsored by SGI - -- Ported to kernel 2.3.35-pre1 - -- Created <devfs_get_name> -=============================================================================== -Changes for patch v152 - -Work sponsored by SGI - -- Updated sample modules.conf - -- Ported to kernel 2.3.36-pre1 -=============================================================================== -Changes for patch v153 - -Work sponsored by SGI - -- Ported to kernel 2.3.42 - -- Removed <devfs_fill_file> -=============================================================================== -Changes for patch v154 - -Work sponsored by SGI - -- Took account of device number changes for /dev/fb* -=============================================================================== -Changes for patch v155 - -Work sponsored by SGI - -- Ported to kernel 2.3.43-pre8 - -- Moved /dev/tty0 to /dev/vc/0 - -- Moved sequence number formatting from <_tty_make_name> to drivers -=============================================================================== -Changes for patch v156 - -Work sponsored by SGI - -- Fixed breakage in drivers/scsi/sd.c due to recent SCSI changes -=============================================================================== -Changes for patch v157 - -Work sponsored by SGI - -- Ported to kernel 2.3.45 -=============================================================================== -Changes for patch v158 - -Work sponsored by SGI - -- Ported to kernel 2.3.46-pre2 -=============================================================================== -Changes for patch v159 - -Work sponsored by SGI - -- Fixed drivers/block/md.c - Thanks to Mike Galbraith <mikeg@weiden.de> - -- Documentation fixes - -- Moved device registration from <lp_init> to <lp_register> - Thanks to Tim Waugh <twaugh@redhat.com> -=============================================================================== -Changes for patch v160 - -Work sponsored by SGI - -- Fixed drivers/char/joystick/joystick.c - Thanks to Vojtech Pavlik <vojtech@suse.cz> - -- Documentation updates - -- Fixed arch/i386/kernel/mtrr.c if procfs and devfs not enabled - -- Fixed drivers/char/stallion.c -=============================================================================== -Changes for patch v161 - -Work sponsored by SGI - -- Remove /dev/ide when ide-mod is unloaded - -- Fixed bug in drivers/block/ide-probe.c when secondary but no primary - -- Added DEVFS_FL_NO_PERSISTENCE flag - -- Used new DEVFS_FL_NO_PERSISTENCE flag for Unix98 pty slaves - -- Removed unnecessary call to <update_devfs_inode_from_entry> in - <devfs_readdir> - -- Only set auto-ownership for /dev/pty/s* -=============================================================================== -Changes for patch v162 - -Work sponsored by SGI - -- Set inode->i_size to correct size for symlinks - Thanks to Jeremy Fitzhardinge <jeremy@goop.org> - -- Only give lookup() method to directories to comply with new VFS - assumptions - -- Remove unnecessary tests in symlink methods - -- Don't kill existing block ops in <devfs_read_inode> - -- Restore auto-ownership for /dev/pty/m* -=============================================================================== -Changes for patch v163 - -Work sponsored by SGI - -- Don't create missing directories in <devfs_find_handle> - -- Removed Documentation/filesystems/devfs/mk-devlinks - -- Updated Documentation/filesystems/devfs/README -=============================================================================== -Changes for patch v164 - -Work sponsored by SGI - -- Fixed CONFIG_DEVFS breakage in drivers/char/serial.c introduced in - linux-2.3.99-pre6-7 -=============================================================================== -Changes for patch v165 - -Work sponsored by SGI - -- Ported to kernel 2.3.99-pre6 -=============================================================================== -Changes for patch v166 - -Work sponsored by SGI - -- Added CONFIG_DEVFS_MOUNT -=============================================================================== -Changes for patch v167 - -Work sponsored by SGI - -- Updated Documentation/filesystems/devfs/README - -- Updated sample modules.conf -=============================================================================== -Changes for patch v168 - -Work sponsored by SGI - -- Disabled multi-mount capability (use VFS bindings instead) - -- Updated README from master HTML file -=============================================================================== -Changes for patch v169 - -Work sponsored by SGI - -- Removed multi-mount code - -- Removed compatibility macros: VFS has changed too much -=============================================================================== -Changes for patch v170 - -Work sponsored by SGI - -- Updated README from master HTML file - -- Merged devfs inode into devfs entry -=============================================================================== -Changes for patch v171 - -Work sponsored by SGI - -- Updated sample modules.conf - -- Removed dead code in <devfs_register> which used to call - <free_dentries> - -- Ported to kernel 2.4.0-test2-pre3 -=============================================================================== -Changes for patch v172 - -Work sponsored by SGI - -- Changed interface to <devfs_register> - -- Changed interface to <devfs_register_series> -=============================================================================== -Changes for patch v173 - -Work sponsored by SGI - -- Simplified interface to <devfs_mk_symlink> - -- Simplified interface to <devfs_mk_dir> - -- Simplified interface to <devfs_find_handle> -=============================================================================== -Changes for patch v174 - -Work sponsored by SGI - -- Updated README from master HTML file -=============================================================================== -Changes for patch v175 - -Work sponsored by SGI - -- DocBook update for fs/devfs/base.c - Thanks to Tim Waugh <twaugh@redhat.com> - -- Removed stale fs/tunnel.c (was never used or completed) -=============================================================================== -Changes for patch v176 - -Work sponsored by SGI - -- Updated ToDo list - -- Removed sample modules.conf: now distributed with devfsd - -- Updated README from master HTML file - -- Ported to kernel 2.4.0-test3-pre4 (which had devfs-patch-v174) -=============================================================================== -Changes for patch v177 - -- Updated README from master HTML file - -- Documentation cleanups - -- Ensure <devfs_generate_path> terminates string for root entry - Thanks to Tim Jansen <tim@tjansen.de> - -- Exported <devfs_get_name> to modules - -- Make <devfs_mk_symlink> send events to devfsd - -- Cleaned up option processing in <devfs_setup> - -- Fixed bugs in handling symlinks: could leak or cause Oops - -- Cleaned up directory handling by separating fops - Thanks to Alexander Viro <viro@parcelfarce.linux.theplanet.co.uk> -=============================================================================== -Changes for patch v178 - -- Fixed handling of inverted options in <devfs_setup> -=============================================================================== -Changes for patch v179 - -- Adjusted <try_modload> to account for <devfs_generate_path> fix -=============================================================================== -Changes for patch v180 - -- Fixed !CONFIG_DEVFS_FS stub declaration of <devfs_get_info> -=============================================================================== -Changes for patch v181 - -- Answered question posed by Al Viro and removed his comments from <devfs_open> - -- Moved setting of registered flag after other fields are changed - -- Fixed race between <devfsd_close> and <devfsd_notify_one> - -- Global VFS changes added bogus BKL to devfsd_close(): removed - -- Widened locking in <devfs_readlink> and <devfs_follow_link> - -- Replaced <devfsd_read> stack usage with <devfsd_ioctl> kmalloc - -- Simplified locking in <devfsd_ioctl> and fixed memory leak -=============================================================================== -Changes for patch v182 - -- Created <devfs_*alloc_major> and <devfs_*alloc_devnum> - -- Removed broken devnum allocation and use <devfs_alloc_devnum> - -- Fixed old devnum leak by calling new <devfs_dealloc_devnum> - -- Created <devfs_*alloc_unique_number> - -- Fixed number leak for /dev/cdroms/cdrom%d - -- Fixed number leak for /dev/discs/disc%d -=============================================================================== -Changes for patch v183 - -- Fixed bug in <devfs_setup> which could hang boot process -=============================================================================== -Changes for patch v184 - -- Documentation typo fix for fs/devfs/util.c - -- Fixed drivers/char/stallion.c for devfs - -- Added DEVFSD_NOTIFY_DELETE event - -- Updated README from master HTML file - -- Removed #include <asm/segment.h> from fs/devfs/base.c -=============================================================================== -Changes for patch v185 - -- Made <block_semaphore> and <char_semaphore> in fs/devfs/util.c - private - -- Fixed inode table races by removing it and using inode->u.generic_ip - instead - -- Moved <devfs_read_inode> into <get_vfs_inode> - -- Moved <devfs_write_inode> into <devfs_notify_change> -=============================================================================== -Changes for patch v186 - -- Fixed race in <devfs_do_symlink> for uni-processor - -- Updated README from master HTML file -=============================================================================== -Changes for patch v187 - -- Fixed drivers/char/stallion.c for devfs - -- Fixed drivers/char/rocket.c for devfs - -- Fixed bug in <devfs_alloc_unique_number>: limited to 128 numbers -=============================================================================== -Changes for patch v188 - -- Updated major masks in fs/devfs/util.c up to Linus' "no new majors" - proclamation. Block: were 126 now 122 free, char: were 26 now 19 free - -- Updated README from master HTML file - -- Removed remnant of multi-mount support in <devfs_mknod> - -- Removed unused DEVFS_FL_SHOW_UNREG flag -=============================================================================== -Changes for patch v189 - -- Removed nlink field from struct devfs_inode - -- Removed auto-ownership for /dev/pty/* (BSD ptys) and used - DEVFS_FL_CURRENT_OWNER|DEVFS_FL_NO_PERSISTENCE for /dev/pty/s* (just - like Unix98 pty slaves) and made /dev/pty/m* rw-rw-rw- access -=============================================================================== -Changes for patch v190 - -- Updated README from master HTML file - -- Replaced BKL with global rwsem to protect symlink data (quick and - dirty hack) -=============================================================================== -Changes for patch v191 - -- Replaced global rwsem for symlink with per-link refcount -=============================================================================== -Changes for patch v192 - -- Removed unnecessary #ifdef CONFIG_DEVFS_FS from arch/i386/kernel/mtrr.c - -- Ported to kernel 2.4.10-pre11 - -- Set inode->i_mapping->a_ops for block nodes in <get_vfs_inode> -=============================================================================== -Changes for patch v193 - -- Went back to global rwsem for symlinks (refcount scheme no good) -=============================================================================== -Changes for patch v194 - -- Fixed overrun in <devfs_link> by removing function (not needed) - -- Updated README from master HTML file -=============================================================================== -Changes for patch v195 - -- Fixed buffer underrun in <try_modload> - -- Moved down_read() from <search_for_entry_in_dir> to <find_entry> -=============================================================================== -Changes for patch v196 - -- Fixed race in <devfsd_ioctl> when setting event mask - Thanks to Kari Hurtta <hurtta@leija.mh.fmi.fi> - -- Avoid deadlock in <devfs_follow_link> by using temporary buffer -=============================================================================== -Changes for patch v197 - -- First release of new locking code for devfs core (v1.0) - -- Fixed bug in drivers/cdrom/cdrom.c -=============================================================================== -Changes for patch v198 - -- Discard temporary buffer, now use "%s" for dentry names - -- Don't generate path in <try_modload>: use fake entry instead - -- Use "existing" directory in <_devfs_make_parent_for_leaf> - -- Use slab cache rather than fixed buffer for devfsd events -=============================================================================== -Changes for patch v199 - -- Removed obsolete usage of DEVFS_FL_NO_PERSISTENCE - -- Send DEVFSD_NOTIFY_REGISTERED events in <devfs_mk_dir> - -- Fixed locking bug in <devfs_d_revalidate_wait> due to typo - -- Do not send CREATE, CHANGE, ASYNC_OPEN or DELETE events from devfsd - or children -=============================================================================== -Changes for patch v200 - -- Ported to kernel 2.5.1-pre2 -=============================================================================== -Changes for patch v201 - -- Fixed bug in <devfsd_read>: was dereferencing freed pointer -=============================================================================== -Changes for patch v202 - -- Fixed bug in <devfsd_close>: was dereferencing freed pointer - -- Added process group check for devfsd privileges -=============================================================================== -Changes for patch v203 - -- Use SLAB_ATOMIC in <devfsd_notify_de> from <devfs_d_delete> -=============================================================================== -Changes for patch v204 - -- Removed long obsolete rc.devfs - -- Return old entry in <devfs_mk_dir> for 2.4.x kernels - -- Updated README from master HTML file - -- Increment refcount on module in <check_disc_changed> - -- Created <devfs_get_handle> and exported <devfs_put> - -- Increment refcount on module in <devfs_get_ops> - -- Created <devfs_put_ops> and used where needed to fix races - -- Added clarifying comments in response to preliminary EMC code review - -- Added poisoning to <devfs_put> - -- Improved debugging messages - -- Fixed unregister bugs in drivers/md/lvm-fs.c -=============================================================================== -Changes for patch v205 - -- Corrected (made useful) debugging message in <unregister> - -- Moved <kmem_cache_create> in <mount_devfs_fs> to <init_devfs_fs> - -- Fixed drivers/md/lvm-fs.c to create "lvm" entry - -- Added magic number to guard against scribbling drivers - -- Only return old entry in <devfs_mk_dir> if a directory - -- Defined macros for error and debug messages - -- Updated README from master HTML file -=============================================================================== -Changes for patch v206 - -- Added support for multiple Compaq cpqarray controllers - -- Fixed (rare, old) race in <devfs_lookup> -=============================================================================== -Changes for patch v207 - -- Fixed deadlock bug in <devfs_d_revalidate_wait> - -- Tag VFS deletable in <devfs_mk_symlink> if handle ignored - -- Updated README from master HTML file -=============================================================================== -Changes for patch v208 - -- Added KERN_* to remaining messages - -- Cleaned up declaration of <stat_read> - -- Updated README from master HTML file -=============================================================================== -Changes for patch v209 - -- Updated README from master HTML file - -- Removed silently introduced calls to lock_kernel() and - unlock_kernel() due to recent VFS locking changes. BKL isn't - required in devfs - -- Changed <devfs_rmdir> to allow later additions if not yet empty - -- Added calls to <devfs_register_partitions> in drivers/block/blkpc.c - <add_partition> and <del_partition> - -- Fixed bug in <devfs_alloc_unique_number>: was clearing beyond - bitfield - -- Fixed bitfield data type for <devfs_*alloc_devnum> - -- Made major bitfield type and initialiser 64 bit safe -=============================================================================== -Changes for patch v210 - -- Updated fs/devfs/util.c to fix shift warning on 64 bit machines - Thanks to Anton Blanchard <anton@samba.org> - -- Updated README from master HTML file -=============================================================================== -Changes for patch v211 - -- Do not put miscellaneous character devices in /dev/misc if they - specify their own directory (i.e. contain a '/' character) - -- Copied macro for error messages from fs/devfs/base.c to - fs/devfs/util.c and made use of this macro - -- Removed 2.4.x compatibility code from fs/devfs/base.c -=============================================================================== -Changes for patch v212 - -- Added BKL to <devfs_open> because drivers still need it -=============================================================================== -Changes for patch v213 - -- Protected <scan_dir_for_removable> and <get_removable_partition> - from changing directory contents -=============================================================================== -Changes for patch v214 - -- Switched to ISO C structure field initialisers - -- Switch to set_current_state() and move before add_wait_queue() - -- Updated README from master HTML file - -- Fixed devfs entry leak in <devfs_readdir> when *readdir fails -=============================================================================== -Changes for patch v215 - -- Created <devfs_find_and_unregister> - -- Switched many functions from <devfs_find_handle> to - <devfs_find_and_unregister> - -- Switched many functions from <devfs_find_handle> to <devfs_get_handle> -=============================================================================== -Changes for patch v216 - -- Switched arch/ia64/sn/io/hcl.c from <devfs_find_handle> to - <devfs_get_handle> - -- Removed deprecated <devfs_find_handle> -=============================================================================== -Changes for patch v217 - -- Exported <devfs_find_and_unregister> and <devfs_only> to modules - -- Updated README from master HTML file - -- Fixed module unload race in <devfs_open> -=============================================================================== -Changes for patch v218 - -- Removed DEVFS_FL_AUTO_OWNER flag - -- Switched lingering structure field initialiser to ISO C - -- Added locking when setting/clearing flags - -- Documentation fix in fs/devfs/util.c diff --git a/Documentation/filesystems/devfs/README b/Documentation/filesystems/devfs/README deleted file mode 100644 index aabfba2..0000000 --- a/Documentation/filesystems/devfs/README +++ /dev/null @@ -1,1959 +0,0 @@ -Devfs (Device File System) FAQ - - -Linux Devfs (Device File System) FAQ -Richard Gooch -20-AUG-2002 - - -Document languages: - - - - - - - ------------------------------------------------------------------------------ - -NOTE: the master copy of this document is available online at: - -http://www.atnf.csiro.au/~rgooch/linux/docs/devfs.html -and looks much better than the text version distributed with the -kernel sources. A mirror site is available at: - -http://www.ras.ucalgary.ca/~rgooch/linux/docs/devfs.html - -There is also an optional daemon that may be used with devfs. You can -find out more about it at: - -http://www.atnf.csiro.au/~rgooch/linux/ - -A mailing list is available which you may subscribe to. Send -email -to majordomo@oss.sgi.com with the following line in the -body of the message: -subscribe devfs -To unsubscribe, send the message body: -unsubscribe devfs -instead. The list is archived at - -http://oss.sgi.com/projects/devfs/archive/. - ------------------------------------------------------------------------------ - -Contents - - -What is it? - -Why do it? - -Who else does it? - -How it works - -Operational issues (essential reading) - -Instructions for the impatient -Permissions persistence across reboots -Dealing with drivers without devfs support -All the way with Devfs -Other Issues -Kernel Naming Scheme -Devfsd Naming Scheme -Old Compatibility Names -SCSI Host Probing Issues - - - -Device drivers currently ported - -Allocation of Device Numbers - -Questions and Answers - -Making things work -Alternatives to devfs -What I don't like about devfs -How to report bugs -Strange kernel messages -Compilation problems with devfsd - - -Other resources - -Translations of this document - - ------------------------------------------------------------------------------ - - -What is it? - -Devfs is an alternative to "real" character and block special devices -on your root filesystem. Kernel device drivers can register devices by -name rather than major and minor numbers. These devices will appear in -devfs automatically, with whatever default ownership and -protection the driver specified. A daemon (devfsd) can be used to -override these defaults. Devfs has been in the kernel since 2.3.46. - -NOTE that devfs is entirely optional. If you prefer the old -disc-based device nodes, then simply leave CONFIG_DEVFS_FS=n (the -default). In this case, nothing will change. ALSO NOTE that if you do -enable devfs, the defaults are such that full compatibility is -maintained with the old devices names. - -There are two aspects to devfs: one is the underlying device -namespace, which is a namespace just like any mounted filesystem. The -other aspect is the filesystem code which provides a view of the -device namespace. The reason I make a distinction is because devfs -can be mounted many times, with each mount showing the same device -namespace. Changes made are global to all mounted devfs filesystems. -Also, because the devfs namespace exists without any devfs mounts, you -can easily mount the root filesystem by referring to an entry in the -devfs namespace. - - -The cost of devfs is a small increase in kernel code size and memory -usage. About 7 pages of code (some of that in __init sections) and 72 -bytes for each entry in the namespace. A modest system has only a -couple of hundred device entries, so this costs a few more -pages. Compare this with the suggestion to put /dev on a <a -href="#why-faq-ramdisc">ramdisc. - -On a typical machine, the cost is under 0.2 percent. On a modest -system with 64 MBytes of RAM, the cost is under 0.1 percent. The -accusations of "bloatware" levelled at devfs are not justified. - ------------------------------------------------------------------------------ - - -Why do it? - -There are several problems that devfs addresses. Some of these -problems are more serious than others (depending on your point of -view), and some can be solved without devfs. However, the totality of -these problems really calls out for devfs. - -The choice is a patchwork of inefficient user space solutions, which -are complex and likely to be fragile, or to use a simple and efficient -devfs which is robust. - -There have been many counter-proposals to devfs, all seeking to -provide some of the benefits without actually implementing devfs. So -far there has been an absence of code and no proposed alternative has -been able to provide all the features that devfs does. Further, -alternative proposals require far more complexity in user-space (and -still deliver less functionality than devfs). Some people have the -mantra of reducing "kernel bloat", but don't consider the effects on -user-space. - -A good solution limits the total complexity of kernel-space and -user-space. - - -Major&minor allocation - -The existing scheme requires the allocation of major and minor device -numbers for each and every device. This means that a central -co-ordinating authority is required to issue these device numbers -(unless you're developing a "private" device driver), in order to -preserve uniqueness. Devfs shifts the burden to a namespace. This may -not seem like a huge benefit, but actually it is. Since driver authors -will naturally choose a device name which reflects the functionality -of the device, there is far less potential for namespace conflict. -Solving this requires a kernel change. - -/dev management - -Because you currently access devices through device nodes, these must -be created by the system administrator. For standard devices you can -usually find a MAKEDEV programme which creates all these (hundreds!) -of nodes. This means that changes in the kernel must be reflected by -changes in the MAKEDEV programme, or else the system administrator -creates device nodes by hand. - -The basic problem is that there are two separate databases of -major and minor numbers. One is in the kernel and one is in /dev (or -in a MAKEDEV programme, if you want to look at it that way). This is -duplication of information, which is not good practice. -Solving this requires a kernel change. - -/dev growth - -A typical /dev has over 1200 nodes! Most of these devices simply don't -exist because the hardware is not available. A huge /dev increases the -time to access devices (I'm just referring to the dentry lookup times -and the time taken to read inodes off disc: the next subsection shows -some more horrors). - -An example of how big /dev can grow is if we consider SCSI devices: - -host 6 bits (say up to 64 hosts on a really big machine) -channel 4 bits (say up to 16 SCSI buses per host) -id 4 bits -lun 3 bits -partition 6 bits -TOTAL 23 bits - - -This requires 8 Mega (1024*1024) inodes if we want to store all -possible device nodes. Even if we scrap everything but id,partition -and assume a single host adapter with a single SCSI bus and only one -logical unit per SCSI target (id), that's still 10 bits or 1024 -inodes. Each VFS inode takes around 256 bytes (kernel 2.1.78), so -that's 256 kBytes of inode storage on disc (assuming real inodes take -a similar amount of space as VFS inodes). This is actually not so bad, -because disc is cheap these days. Embedded systems would care about -256 kBytes of /dev inodes, but you could argue that embedded systems -would have hand-tuned /dev directories. I've had to do just that on my -embedded systems, but I would rather just leave it to devfs. - -Another issue is the time taken to lookup an inode when first -referenced. Not only does this take time in scanning through a list in -memory, but also the seek times to read the inodes off disc. -This could be solved in user-space using a clever programme which -scanned the kernel logs and deleted /dev entries which are not -available and created them when they were available. This programme -would need to be run every time a new module was loaded, which would -slow things down a lot. - -There is an existing programme called scsidev which will automatically -create device nodes for SCSI devices. It can do this by scanning files -in /proc/scsi. Unfortunately, to extend this idea to other device -nodes would require significant modifications to existing drivers (so -they too would provide information in /proc). This is a non-trivial -change (I should know: devfs has had to do something similar). Once -you go to this much effort, you may as well use devfs itself (which -also provides this information). Furthermore, such a system would -likely be implemented in an ad-hoc fashion, as different drivers will -provide their information in different ways. - -Devfs is much cleaner, because it (naturally) has a uniform mechanism -to provide this information: the device nodes themselves! - - -Node to driver file_operations translation - -There is an important difference between the way disc-based character -and block nodes and devfs entries make the connection between an entry -in /dev and the actual device driver. - -With the current 8 bit major and minor numbers the connection between -disc-based c&b nodes and per-major drivers is done through a -fixed-length table of 128 entries. The various filesystem types set -the inode operations for c&b nodes to {chr,blk}dev_inode_operations, -so when a device is opened a few quick levels of indirection bring us -to the driver file_operations. - -For miscellaneous character devices a second step is required: there -is a scan for the driver entry with the same minor number as the file -that was opened, and the appropriate minor open method is called. This -scanning is done *every time* you open a device node. Potentially, you -may be searching through dozens of misc. entries before you find your -open method. While not an enormous performance overhead, this does -seem pointless. - -Linux *must* move beyond the 8 bit major and minor barrier, -somehow. If we simply increase each to 16 bits, then the indexing -scheme used for major driver lookup becomes untenable, because the -major tables (one each for character and block devices) would need to -be 64 k entries long (512 kBytes on x86, 1 MByte for 64 bit -systems). So we would have to use a scheme like that used for -miscellaneous character devices, which means the search time goes up -linearly with the average number of major device drivers on your -system. Not all "devices" are hardware, some are higher-level drivers -like KGI, so you can get more "devices" without adding hardware -You can improve this by creating an ordered (balanced:-) -binary tree, in which case your search time becomes log(N). -Alternatively, you can use hashing to speed up the search. -But why do that search at all if you don't have to? Once again, it -seems pointless. - -Note that devfs doesn't use the major&minor system. For devfs -entries, the connection is done when you lookup the /dev entry. When -devfs_register() is called, an internal table is appended which has -the entry name and the file_operations. If the dentry cache doesn't -have the /dev entry already, this internal table is scanned to get the -file_operations, and an inode is created. If the dentry cache already -has the entry, there is *no lookup time* (other than the dentry scan -itself, but we can't avoid that anyway, and besides Linux dentries -cream other OS's which don't have them:-). Furthermore, the number of -node entries in a devfs is only the number of available device -entries, not the number of *conceivable* entries. Even if you remove -unnecessary entries in a disc-based /dev, the number of conceivable -entries remains the same: you just limit yourself in order to save -space. - -Devfs provides a fast connection between a VFS node and the device -driver, in a scalable way. - -/dev as a system administration tool - -Right now /dev contains a list of conceivable devices, most of which I -don't have. Devfs only shows those devices available on my -system. This means that listing /dev is a handy way of checking what -devices are available. - -Major&minor size - -Existing major and minor numbers are limited to 8 bits each. This is -now a limiting factor for some drivers, particularly the SCSI disc -driver, which consumes a single major number. Only 16 discs are -supported, and each disc may have only 15 partitions. Maybe this isn't -a problem for you, but some of us are building huge Linux systems with -disc arrays. With devfs an arbitrary pointer can be associated with -each device entry, which can be used to give an effective 32 bit -device identifier (i.e. that's like having a 32 bit minor -number). Since this is private to the kernel, there are no C library -compatibility issues which you would have with increasing major and -minor number sizes. See the section on "Allocation of Device Numbers" -for details on maintaining compatibility with userspace. - -Solving this requires a kernel change. - -Since writing this, the kernel has been modified so that the SCSI disc -driver has more major numbers allocated to it and now supports up to -128 discs. Since these major numbers are non-contiguous (a result of -unplanned expansion), the implementation is a little more cumbersome -than originally. - -Just like the changes to IPv4 to fix impending limitations in the -address space, people find ways around the limitations. In the long -run, however, solutions like IPv6 or devfs can't be put off forever. - -Read-only root filesystem - -Having your device nodes on the root filesystem means that you can't -operate properly with a read-only root filesystem. This is because you -want to change ownerships and protections of tty devices. Existing -practice prevents you using a CD-ROM as your root filesystem for a -*real* system. Sure, you can boot off a CD-ROM, but you can't change -tty ownerships, so it's only good for installing. - -Also, you can't use a shared NFS root filesystem for a cluster of -discless Linux machines (having tty ownerships changed on a common -/dev is not good). Nor can you embed your root filesystem in a -ROM-FS. - -You can get around this by creating a RAMDISC at boot time, making -an ext2 filesystem in it, mounting it somewhere and copying the -contents of /dev into it, then unmounting it and mounting it over -/dev. - -A devfs is a cleaner way of solving this. - -Non-Unix root filesystem - -Non-Unix filesystems (such as NTFS) can't be used for a root -filesystem because they variously don't support character and block -special files or symbolic links. You can't have a separate disc-based -or RAMDISC-based filesystem mounted on /dev because you need device -nodes before you can mount these. Devfs can be mounted without any -device nodes. Devlinks won't work because symlinks aren't supported. -An alternative solution is to use initrd to mount a RAMDISC initial -root filesystem (which is populated with a minimal set of device -nodes), and then construct a new /dev in another RAMDISC, and finally -switch to your non-Unix root filesystem. This requires clever boot -scripts and a fragile and conceptually complex boot procedure. - -Devfs solves this in a robust and conceptually simple way. - -PTY security - -Current pseudo-tty (pty) devices are owned by root and read-writable -by everyone. The user of a pty-pair cannot change -ownership/protections without being suid-root. - -This could be solved with a secure user-space daemon which runs as -root and does the actual creation of pty-pairs. Such a daemon would -require modification to *every* programme that wants to use this new -mechanism. It also slows down creation of pty-pairs. - -An alternative is to create a new open_pty() syscall which does much -the same thing as the user-space daemon. Once again, this requires -modifications to pty-handling programmes. - -The devfs solution allows a device driver to "tag" certain device -files so that when an unopened device is opened, the ownerships are -changed to the current euid and egid of the opening process, and the -protections are changed to the default registered by the driver. When -the device is closed ownership is set back to root and protections are -set back to read-write for everybody. No programme need be changed. -The devpts filesystem provides this auto-ownership feature for Unix98 -ptys. It doesn't support old-style pty devices, nor does it have all -the other features of devfs. - -Intelligent device management - -Devfs implements a simple yet powerful protocol for communication with -a device management daemon (devfsd) which runs in user space. It is -possible to send a message (either synchronously or asynchronously) to -devfsd on any event, such as registration/unregistration of device -entries, opening and closing devices, looking up inodes, scanning -directories and more. This has many possibilities. Some of these are -already implemented. See: - - -http://www.atnf.csiro.au/~rgooch/linux/ - -Device entry registration events can be used by devfsd to change -permissions of newly-created device nodes. This is one mechanism to -control device permissions. - -Device entry registration/unregistration events can be used to run -programmes or scripts. This can be used to provide automatic mounting -of filesystems when a new block device media is inserted into the -drive. - -Asynchronous device open and close events can be used to implement -clever permissions management. For example, the default permissions on -/dev/dsp do not allow everybody to read from the device. This is -sensible, as you don't want some remote user recording what you say at -your console. However, the console user is also prevented from -recording. This behaviour is not desirable. With asynchronous device -open and close events, you can have devfsd run a programme or script -when console devices are opened to change the ownerships for *other* -device nodes (such as /dev/dsp). On closure, you can run a different -script to restore permissions. An advantage of this scheme over -modifying the C library tty handling is that this works even if your -programme crashes (how many times have you seen the utmp database with -lingering entries for non-existent logins?). - -Synchronous device open events can be used to perform intelligent -device access protections. Before the device driver open() method is -called, the daemon must first validate the open attempt, by running an -external programme or script. This is far more flexible than access -control lists, as access can be determined on the basis of other -system conditions instead of just the UID and GID. - -Inode lookup events can be used to authenticate module autoload -requests. Instead of using kmod directly, the event is sent to -devfsd which can implement an arbitrary authentication before loading -the module itself. - -Inode lookup events can also be used to construct arbitrary -namespaces, without having to resort to populating devfs with symlinks -to devices that don't exist. - -Speculative Device Scanning - -Consider an application (like cdparanoia) that wants to find all -CD-ROM devices on the system (SCSI, IDE and other types), whether or -not their respective modules are loaded. The application must -speculatively open certain device nodes (such as /dev/sr0 for the SCSI -CD-ROMs) in order to make sure the module is loaded. This requires -that all Linux distributions follow the standard device naming scheme -(last time I looked RedHat did things differently). Devfs solves the -naming problem. - -The same application also wants to see which devices are actually -available on the system. With the existing system it needs to read the -/dev directory and speculatively open each /dev/sr* device to -determine if the device exists or not. With a large /dev this is an -inefficient operation, especially if there are many /dev/sr* nodes. A -solution like scsidev could reduce the number of /dev/sr* entries (but -of course that also requires all that inefficient directory scanning). - -With devfs, the application can open the /dev/sr directory -(which triggers the module autoloading if required), and proceed to -read /dev/sr. Since only the available devices will have -entries, there are no inefficencies in directory scanning or device -openings. - ------------------------------------------------------------------------------ - -Who else does it? - -FreeBSD has a devfs implementation. Solaris and AIX each have a -pseudo-devfs (something akin to scsidev but for all devices, with some -unspecified kernel support). BeOS, Plan9 and QNX also have it. SGI's -IRIX 6.4 and above also have a device filesystem. - -While we shouldn't just automatically do something because others do -it, we should not ignore the work of others either. FreeBSD has a lot -of competent people working on it, so their opinion should not be -blithely ignored. - ------------------------------------------------------------------------------ - - -How it works - -Registering device entries - -For every entry (device node) in a devfs-based /dev a driver must call -devfs_register(). This adds the name of the device entry, the -file_operations structure pointer and a few other things to an -internal table. Device entries may be added and removed at any -time. When a device entry is registered, it automagically appears in -any mounted devfs'. - -Inode lookup - -When a lookup operation on an entry is performed and if there is no -driver information for that entry devfs will attempt to call -devfsd. If still no driver information can be found then a negative -dentry is yielded and the next stage operation will be called by the -VFS (such as create() or mknod() inode methods). If driver information -can be found, an inode is created (if one does not exist already) and -all is well. - -Manually creating device nodes - -The mknod() method allows you to create an ordinary named pipe in the -devfs, or you can create a character or block special inode if one -does not already exist. You may wish to create a character or block -special inode so that you can set permissions and ownership. Later, if -a device driver registers an entry with the same name, the -permissions, ownership and times are retained. This is how you can set -the protections on a device even before the driver is loaded. Once you -create an inode it appears in the directory listing. - -Unregistering device entries - -A device driver calls devfs_unregister() to unregister an entry. - -Chroot() gaols - -2.2.x kernels - -The semantics of inode creation are different when devfs is mounted -with the "explicit" option. Now, when a device entry is registered, it -will not appear until you use mknod() to create the device. It doesn't -matter if you mknod() before or after the device is registered with -devfs_register(). The purpose of this behaviour is to support -chroot(2) gaols, where you want to mount a minimal devfs inside the -gaol. Only the devices you specifically want to be available (through -your mknod() setup) will be accessible. - -2.4.x kernels - -As of kernel 2.3.99, the VFS has had the ability to rebind parts of -the global filesystem namespace into another part of the namespace. -This now works even at the leaf-node level, which means that -individual files and device nodes may be bound into other parts of the -namespace. This is like making links, but better, because it works -across filesystems (unlike hard links) and works through chroot() -gaols (unlike symbolic links). - -Because of these improvements to the VFS, the multi-mount capability -in devfs is no longer needed. The administrator may create a minimal -device tree inside a chroot(2) gaol by using VFS bindings. As this -provides most of the features of the devfs multi-mount capability, I -removed the multi-mount support code (after issuing an RFC). This -yielded code size reductions and simplifications. - -If you want to construct a minimal chroot() gaol, the following -command should suffice: - -mount --bind /dev/null /gaol/dev/null - - -Repeat for other device nodes you want to expose. Simple! - ------------------------------------------------------------------------------ - - -Operational issues - - -Instructions for the impatient - -Nobody likes reading documentation. People just want to get in there -and play. So this section tells you quickly the steps you need to take -to run with devfs mounted over /dev. Skip these steps and you will end -up with a nearly unbootable system. Subsequent sections describe the -issues in more detail, and discuss non-essential configuration -options. - -Devfsd -OK, if you're reading this, I assume you want to play with -devfs. First you should ensure that /usr/src/linux contains a -recent kernel source tree. Then you need to compile devfsd, the device -management daemon, available at - -http://www.atnf.csiro.au/~rgooch/linux/. -Because the kernel has a naming scheme -which is quite different from the old naming scheme, you need to -install devfsd so that software and configuration files that use the -old naming scheme will not break. - -Compile and install devfsd. You will be provided with a default -configuration file /etc/devfsd.conf which will provide -compatibility symlinks for the old naming scheme. Don't change this -config file unless you know what you're doing. Even if you think you -do know what you're doing, don't change it until you've followed all -the steps below and booted a devfs-enabled system and verified that it -works. - -Now edit your main system boot script so that devfsd is started at the -very beginning (before any filesystem -checks). /etc/rc.d/rc.sysinit is often the main boot script -on systems with SysV-style boot scripts. On systems with BSD-style -boot scripts it is often /etc/rc. Also check -/sbin/rc. - -NOTE that the line you put into the boot -script should be exactly: - -/sbin/devfsd /dev - -DO NOT use some special daemon-launching -programme, otherwise the boot script may not wait for devfsd to finish -initialising. - -System Libraries -There may still be some problems because of broken software making -assumptions about device names. In particular, some software does not -handle devices which are symbolic links. If you are running a libc 5 -based system, install libc 5.4.44 (if you have libc 5.4.46, go back to -libc 5.4.44, which is actually correct). If you are running a glibc -based system, make sure you have glibc 2.1.3 or later. - -/etc/securetty -PAM (Pluggable Authentication Modules) is supposed to be a flexible -mechanism for providing better user authentication and access to -services. Unfortunately, it's also fragile, complex and undocumented -(check out RedHat 6.1, and probably other distributions as well). PAM -has problems with symbolic links. Append the following lines to your -/etc/securetty file: - -vc/1 -vc/2 -vc/3 -vc/4 -vc/5 -vc/6 -vc/7 -vc/8 - -This will not weaken security. If you have a version of util-linux -earlier than 2.10.h, please upgrade to 2.10.h or later. If you -absolutely cannot upgrade, then also append the following lines to -your /etc/securetty file: - -1 -2 -3 -4 -5 -6 -7 -8 - -This may potentially weaken security by allowing root logins over the -network (a password is still required, though). However, since there -are problems with dealing with symlinks, I'm suspicious of the level -of security offered in any case. - -XFree86 -While not essential, it's probably a good idea to upgrade to XFree86 -4.0, as patches went in to make it more devfs-friendly. If you don't, -you'll probably need to apply the following patch to -/etc/security/console.perms so that ordinary users can run -startx. Note that not all distributions have this file (e.g. Debian), -so if it's not present, don't worry about it. - ---- /etc/security/console.perms.orig Sat Apr 17 16:26:47 1999 -+++ /etc/security/console.perms Fri Feb 25 23:53:55 2000 -@@ -14,7 +14,7 @@ - # man 5 console.perms - - # file classes -- these are regular expressions --<console>=tty[0-9][0-9]* :[0-9]\.[0-9] :[0-9] -+<console>=tty[0-9][0-9]* vc/[0-9][0-9]* :[0-9]\.[0-9] :[0-9] - - # device classes -- these are shell-style globs - <floppy>=/dev/fd[0-1]* - -If the patch does not apply, then change the line: - -<console>=tty[0-9][0-9]* :[0-9]\.[0-9] :[0-9] - -with: - -<console>=tty[0-9][0-9]* vc/[0-9][0-9]* :[0-9]\.[0-9] :[0-9] - - -Disable devpts -I've had a report of devpts mounted on /dev/pts not working -correctly. Since devfs will also manage /dev/pts, there is no -need to mount devpts as well. You should either edit your -/etc/fstab so devpts is not mounted, or disable devpts from -your kernel configuration. - -Unsupported drivers -Not all drivers have devfs support. If you depend on one of these -drivers, you will need to create a script or tarfile that you can use -at boot time to create device nodes as appropriate. There is a -section which describes this. Another -section lists the drivers which have -devfs support. - -/dev/mouse - -Many disributions configure /dev/mouse to be the mouse device -for XFree86 and GPM. I actually think this is a bad idea, because it -adds another level of indirection. When looking at a config file, if -you see /dev/mouse you're left wondering which mouse -is being referred to. Hence I recommend putting the actual mouse -device (for example /dev/psaux) into your -/etc/X11/XF86Config file (and similarly for the GPM -configuration file). - -Alternatively, use the same technique used for unsupported drivers -described above. - -The Kernel -Finally, you need to make sure devfs is compiled into your kernel. Set -CONFIG_EXPERIMENTAL=y, CONFIG_DEVFS_FS=y and CONFIG_DEVFS_MOUNT=y by -using favourite configuration tool (i.e. make config or -make xconfig) and then make clean and then recompile your kernel and -modules. At boot, devfs will be mounted onto /dev. - -If you encounter problems booting (for example if you forgot a -configuration step), you can pass devfs=nomount at the kernel -boot command line. This will prevent the kernel from mounting devfs at -boot time onto /dev. - -In general, a kernel built with CONFIG_DEVFS_FS=y but without mounting -devfs onto /dev is completely safe, and requires no -configuration changes. One exception to take note of is when -LABEL= directives are used in /etc/fstab. In this -case you will be unable to boot properly. This is because the -mount(8) programme uses /proc/partitions as part of -the volume label search process, and the device names it finds are not -available, because setting CONFIG_DEVFS_FS=y changes the names in -/proc/partitions, irrespective of whether devfs is mounted. - -Now you've finished all the steps required. You're now ready to boot -your shiny new kernel. Enjoy. - -Changing the configuration - -OK, you've now booted a devfs-enabled system, and everything works. -Now you may feel like changing the configuration (common targets are -/etc/fstab and /etc/devfsd.conf). Since you have a -system that works, if you make any changes and it doesn't work, you -now know that you only have to restore your configuration files to the -default and it will work again. - - -Permissions persistence across reboots - -If you don't use mknod(2) to create a device file, nor use chmod(2) or -chown(2) to change the ownerships/permissions, the inode ctime will -remain at 0 (the epoch, 12 am, 1-JAN-1970, GMT). Anything with a ctime -later than this has had it's ownership/permissions changed. Hence, a -simple script or programme may be used to tar up all changed inodes, -prior to shutdown. Although effective, many consider this approach a -kludge. - -A much better approach is to use devfsd to save and restore -permissions. It may be configured to record changes in permissions and -will save them in a database (in fact a directory tree), and restore -these upon boot. This is an efficient method and results in immediate -saving of current permissions (unlike the tar approach, which saves -permissions at some unspecified future time). - -The default configuration file supplied with devfsd has config entries -which you may uncomment to enable persistence management. - -If you decide to use the tar approach anyway, be aware that tar will -first unlink(2) an inode before creating a new device node. The -unlink(2) has the effect of breaking the connection between a devfs -entry and the device driver. If you use the "devfs=only" boot option, -you lose access to the device driver, requiring you to reload the -module. I consider this a bug in tar (there is no real need to -unlink(2) the inode first). - -Alternatively, you can use devfsd to provide more sophisticated -management of device permissions. You can use devfsd to store -permissions for whole groups of devices with a single configuration -entry, rather than the conventional single entry per device entry. - -Permissions database stored in mounted-over /dev - -If you wish to save and restore your device permissions into the -disc-based /dev while still mounting devfs onto /dev -you may do so. This requires a 2.4.x kernel (in fact, 2.3.99 or -later), which has the VFS binding facility. You need to do the -following to set this up: - - - -make sure the kernel does not mount devfs at boot time - - -make sure you have a correct /dev/console entry in your -root file-system (where your disc-based /dev lives) - -create the /dev-state directory - - -add the following lines near the very beginning of your boot -scripts: - -mount --bind /dev /dev-state -mount -t devfs none /dev -devfsd /dev - - - - -add the following lines to your /etc/devfsd.conf file: - -REGISTER ^pt[sy] IGNORE -CREATE ^pt[sy] IGNORE -CHANGE ^pt[sy] IGNORE -DELETE ^pt[sy] IGNORE -REGISTER .* COPY /dev-state/$devname $devpath -CREATE .* COPY $devpath /dev-state/$devname -CHANGE .* COPY $devpath /dev-state/$devname -DELETE .* CFUNCTION GLOBAL unlink /dev-state/$devname -RESTORE /dev-state - -Note that the sample devfsd.conf file contains these lines, -as well as other sample configurations you may find useful. See the -devfsd distribution - - -reboot. - - - - -Permissions database stored in normal directory - -If you are using an older kernel which doesn't support VFS binding, -then you won't be able to have the permissions database in a -mounted-over /dev. However, you can still use a regular -directory to store the database. The sample /etc/devfsd.conf -file above may still be used. You will need to create the -/dev-state directory prior to installing devfsd. If you have -old permissions in /dev, then just copy (or move) the device -nodes over to the new directory. - -Which method is better? - -The best method is to have the permissions database stored in the -mounted-over /dev. This is because you will not need to copy -device nodes over to /dev-state, and because it allows you to -switch between devfs and non-devfs kernels, without requiring you to -copy permissions between /dev-state (for devfs) and -/dev (for non-devfs). - - -Dealing with drivers without devfs support - -Currently, not all device drivers in the kernel have been modified to -use devfs. Device drivers which do not yet have devfs support will not -automagically appear in devfs. The simplest way to create device nodes -for these drivers is to unpack a tarfile containing the required -device nodes. You can do this in your boot scripts. All your drivers -will now work as before. - -Hopefully for most people devfs will have enough support so that they -can mount devfs directly over /dev without losing most functionality -(i.e. losing access to various devices). As of 22-JAN-1998 (devfs -patch version 10) I am now running this way. All the devices I have -are available in devfs, so I don't lose anything. - -WARNING: if your configuration requires the old-style device names -(i.e. /dev/hda1 or /dev/sda1), you must install devfsd and configure -it to maintain compatibility entries. It is almost certain that you -will require this. Note that the kernel creates a compatibility entry -for the root device, so you don't need initrd. - -Note that you no longer need to mount devpts if you use Unix98 PTYs, -as devfs can manage /dev/pts itself. This saves you some RAM, as you -don't need to compile and install devpts. Note that some versions of -glibc have a bug with Unix98 pty handling on devfs systems. Contact -the glibc maintainers for a fix. Glibc 2.1.3 has the fix. - -Note also that apart from editing /etc/fstab, other things will need -to be changed if you *don't* install devfsd. Some software (like the X -server) hard-wire device names in their source. It really is much -easier to install devfsd so that compatibility entries are created. -You can then slowly migrate your system to using the new device names -(for example, by starting with /etc/fstab), and then limiting the -compatibility entries that devfsd creates. - -IF YOU CONFIGURE TO MOUNT DEVFS AT BOOT, MAKE SURE YOU INSTALL DEVFSD -BEFORE YOU BOOT A DEVFS-ENABLED KERNEL! - -Now that devfs has gone into the 2.3.46 kernel, I'm getting a lot of -reports back. Many of these are because people are trying to run -without devfsd, and hence some things break. Please just run devfsd if -things break. I want to concentrate on real bugs rather than -misconfiguration problems at the moment. If people are willing to fix -bugs/false assumptions in other code (i.e. glibc, X server) and submit -that to the respective maintainers, that would be great. - - -All the way with Devfs - -The devfs kernel patch creates a rationalised device tree. As stated -above, if you want to keep using the old /dev naming scheme, -you just need to configure devfsd appopriately (see the man -page). People who prefer the old names can ignore this section. For -those of us who like the rationalised names and an uncluttered -/dev, read on. - -If you don't run devfsd, or don't enable compatibility entry -management, then you will have to configure your system to use the new -names. For example, you will then need to edit your -/etc/fstab to use the new disc naming scheme. If you want to -be able to boot non-devfs kernels, you will need compatibility -symlinks in the underlying disc-based /dev pointing back to -the old-style names for when you boot a kernel without devfs. - -You can selectively decide which devices you want compatibility -entries for. For example, you may only want compatibility entries for -BSD pseudo-terminal devices (otherwise you'll have to patch you C -library or use Unix98 ptys instead). It's just a matter of putting in -the correct regular expression into /dev/devfsd.conf. - -There are other choices of naming schemes that you may prefer. For -example, I don't use the kernel-supplied -names, because they are too verbose. A common misconception is -that the kernel-supplied names are meant to be used directly in -configuration files. This is not the case. They are designed to -reflect the layout of the devices attached and to provide easy -classification. - -If you like the kernel-supplied names, that's fine. If you don't then -you should be using devfsd to construct a namespace more to your -liking. Devfsd has built-in code to construct a -namespace that is both logical and easy to -manage. In essence, it creates a convenient abbreviation of the -kernel-supplied namespace. - -You are of course free to build your own namespace. Devfsd has all the -infrastructure required to make this easy for you. All you need do is -write a script. You can even write some C code and devfsd can load the -shared object as a callable extension. - - -Other Issues - -The init programme -Another thing to take note of is whether your init programme -creates a Unix socket /dev/telinit. Some versions of init -create /dev/telinit so that the telinit programme can -communicate with the init process. If you have such a system you need -to make sure that devfs is mounted over /dev *before* init -starts. In other words, you can't leave the mounting of devfs to -/etc/rc, since this is executed after init. Other -versions of init require a named pipe /dev/initctl -which must exist *before* init starts. Once again, you need to -mount devfs and then create the named pipe *before* init -starts. - -The default behaviour now is not to mount devfs onto /dev at -boot time for 2.3.x and later kernels. You can correct this with the -"devfs=mount" boot option. This solves any problems with init, -and also prevents the dreaded: - -Cannot open initial console - -message. For 2.2.x kernels where you need to apply the devfs patch, -the default is to mount. - -If you have automatic mounting of devfs onto /dev then you -may need to create /dev/initctl in your boot scripts. The -following lines should suffice: - -mknod /dev/initctl p -kill -SIGUSR1 1 # tell init that /dev/initctl now exists - -Alternatively, if you don't want the kernel to mount devfs onto -/dev then you could use the following procedure is a -guideline for how to get around /dev/initctl problems: - -# cd /sbin -# mv init init.real -# cat > init -#! /bin/sh -mount -n -t devfs none /dev -mknod /dev/initctl p -exec /sbin/init.real $* -[control-D] -# chmod a+x init - -Note that newer versions of init create /dev/initctl -automatically, so you don't have to worry about this. - -Module autoloading -You will need to configure devfsd to enable module -autoloading. The following lines should be placed in your -/etc/devfsd.conf file: - -LOOKUP .* MODLOAD - - -As of devfsd-v1.3.10, a generic /etc/modules.devfs -configuration file is installed, which is used by the MODLOAD -action. This should be sufficient for most configurations. If you -require further configuration, edit your /etc/modules.conf -file. The way module autoloading work with devfs is: - - -a process attempts to lookup a device node (e.g. /dev/fred) - - -if that device node does not exist, the full pathname is passed to -devfsd as a string - - -devfsd will pass the string to the modprobe programme (provided the -configuration line shown above is present), and specifies that -/etc/modules.devfs is the configuration file - - -/etc/modules.devfs includes /etc/modules.conf to -access local configurations - -modprobe will search it's configuration files, looking for an alias -that translates the pathname into a module name - - -the translated pathname is then used to load the module. - - -If you wanted a lookup of /dev/fred to load the -mymod module, you would require the following configuration -line in /etc/modules.conf: - -alias /dev/fred mymod - -The /etc/modules.devfs configuration file provides many such -aliases for standard device names. If you look closely at this file, -you will note that some modules require multiple alias configuration -lines. This is required to support module autoloading for old and new -device names. - -Mounting root off a devfs device -If you wish to mount root off a devfs device when you pass the -"devfs=only" boot option, then you need to pass in the -"root=<device>" option to the kernel when booting. If you use -LILO, then you must have this in lilo.conf: - -append = "root=<device>" - -Surprised? Yep, so was I. It turns out if you have (as most people -do): - -root = <device> - - -then LILO will determine the device number of <device> and will -write that device number into a special place in the kernel image -before starting the kernel, and the kernel will use that device number -to mount the root filesystem. So, using the "append" variety ensures -that LILO passes the root filesystem device as a string, which devfs -can then use. - -Note that this isn't an issue if you don't pass "devfs=only". - -TTY issues -The ttyname(3) function in some versions of the C library makes -false assumptions about device entries which are symbolic links. The -tty(1) programme is one that depends on this function. I've -written a patch to libc 5.4.43 which fixes this. This has been -included in libc 5.4.44 and a similar fix is in glibc 2.1.3. - - -Kernel Naming Scheme - -The kernel provides a default naming scheme. This scheme is designed -to make it easy to search for specific devices or device types, and to -view the available devices. Some device types (such as hard discs), -have a directory of entries, making it easy to see what devices of -that class are available. Often, the entries are symbolic links into a -directory tree that reflects the topology of available devices. The -topological tree is useful for finding how your devices are arranged. - -Below is a list of the naming schemes for the most common drivers. A -list of reserved device names is -available for reference. Please send email to -rgooch@atnf.csiro.au to obtain an allocation. Please be -patient (the maintainer is busy). An alternative name may be allocated -instead of the requested name, at the discretion of the maintainer. - -Disc Devices - -All discs, whether SCSI, IDE or whatever, are placed under the -/dev/discs hierarchy: - - /dev/discs/disc0 first disc - /dev/discs/disc1 second disc - - -Each of these entries is a symbolic link to the directory for that -device. The device directory contains: - - disc for the whole disc - part* for individual partitions - - -CD-ROM Devices - -All CD-ROMs, whether SCSI, IDE or whatever, are placed under the -/dev/cdroms hierarchy: - - /dev/cdroms/cdrom0 first CD-ROM - /dev/cdroms/cdrom1 second CD-ROM - - -Each of these entries is a symbolic link to the real device entry for -that device. - -Tape Devices - -All tapes, whether SCSI, IDE or whatever, are placed under the -/dev/tapes hierarchy: - - /dev/tapes/tape0 first tape - /dev/tapes/tape1 second tape - - -Each of these entries is a symbolic link to the directory for that -device. The device directory contains: - - mt for mode 0 - mtl for mode 1 - mtm for mode 2 - mta for mode 3 - mtn for mode 0, no rewind - mtln for mode 1, no rewind - mtmn for mode 2, no rewind - mtan for mode 3, no rewind - - -SCSI Devices - -To uniquely identify any SCSI device requires the following -information: - - controller (host adapter) - bus (SCSI channel) - target (SCSI ID) - unit (Logical Unit Number) - - -All SCSI devices are placed under /dev/scsi (assuming devfs -is mounted on /dev). Hence, a SCSI device with the following -parameters: c=1,b=2,t=3,u=4 would appear as: - - /dev/scsi/host1/bus2/target3/lun4 device directory - - -Inside this directory, a number of device entries may be created, -depending on which SCSI device-type drivers were installed. - -See the section on the disc naming scheme to see what entries the SCSI -disc driver creates. - -See the section on the tape naming scheme to see what entries the SCSI -tape driver creates. - -The SCSI CD-ROM driver creates: - - cd - - -The SCSI generic driver creates: - - generic - - -IDE Devices - -To uniquely identify any IDE device requires the following -information: - - controller - bus (aka. primary/secondary) - target (aka. master/slave) - unit - - -All IDE devices are placed under /dev/ide, and uses a similar -naming scheme to the SCSI subsystem. - -XT Hard Discs - -All XT discs are placed under /dev/xd. The first XT disc has -the directory /dev/xd/disc0. - -TTY devices - -The tty devices now appear as: - - New name Old-name Device Type - -------- -------- ----------- - /dev/tts/{0,1,...} /dev/ttyS{0,1,...} Serial ports - /dev/cua/{0,1,...} /dev/cua{0,1,...} Call out devices - /dev/vc/0 /dev/tty Current virtual console - /dev/vc/{1,2,...} /dev/tty{1...63} Virtual consoles - /dev/vcc/{0,1,...} /dev/vcs{1...63} Virtual consoles - /dev/pty/m{0,1,...} /dev/ptyp?? PTY masters - /dev/pty/s{0,1,...} /dev/ttyp?? PTY slaves - - -RAMDISCS - -The RAMDISCS are placed in their own directory, and are named thus: - - /dev/rd/{0,1,2,...} - - -Meta Devices - -The meta devices are placed in their own directory, and are named -thus: - - /dev/md/{0,1,2,...} - - -Floppy discs - -Floppy discs are placed in the /dev/floppy directory. - -Loop devices - -Loop devices are placed in the /dev/loop directory. - -Sound devices - -Sound devices are placed in the /dev/sound directory -(audio, sequencer, ...). - - -Devfsd Naming Scheme - -Devfsd provides a naming scheme which is a convenient abbreviation of -the kernel-supplied namespace. In some -cases, the kernel-supplied naming scheme is quite convenient, so -devfsd does not provide another naming scheme. The convenience names -that devfsd creates are in fact the same names as the original devfs -kernel patch created (before Linus mandated the Big Name -Change). These are referred to as "new compatibility entries". - -In order to configure devfsd to create these convenience names, the -following lines should be placed in your /etc/devfsd.conf: - -REGISTER .* MKNEWCOMPAT -UNREGISTER .* RMNEWCOMPAT - -This will cause devfsd to create (and destroy) symbolic links which -point to the kernel-supplied names. - -SCSI Hard Discs - -All SCSI discs are placed under /dev/sd (assuming devfs is -mounted on /dev). Hence, a SCSI disc with the following -parameters: c=1,b=2,t=3,u=4 would appear as: - - /dev/sd/c1b2t3u4 for the whole disc - /dev/sd/c1b2t3u4p5 for the 5th partition - /dev/sd/c1b2t3u4p5s6 for the 6th slice in the 5th partition - - -SCSI Tapes - -All SCSI tapes are placed under /dev/st. A similar naming -scheme is used as for SCSI discs. A SCSI tape with the -parameters:c=1,b=2,t=3,u=4 would appear as: - - /dev/st/c1b2t3u4m0 for mode 0 - /dev/st/c1b2t3u4m1 for mode 1 - /dev/st/c1b2t3u4m2 for mode 2 - /dev/st/c1b2t3u4m3 for mode 3 - /dev/st/c1b2t3u4m0n for mode 0, no rewind - /dev/st/c1b2t3u4m1n for mode 1, no rewind - /dev/st/c1b2t3u4m2n for mode 2, no rewind - /dev/st/c1b2t3u4m3n for mode 3, no rewind - - -SCSI CD-ROMs - -All SCSI CD-ROMs are placed under /dev/sr. A similar naming -scheme is used as for SCSI discs. A SCSI CD-ROM with the -parameters:c=1,b=2,t=3,u=4 would appear as: - - /dev/sr/c1b2t3u4 - - -SCSI Generic Devices - -The generic (aka. raw) interface for all SCSI devices are placed under -/dev/sg. A similar naming scheme is used as for SCSI discs. A -SCSI generic device with the parameters:c=1,b=2,t=3,u=4 would appear -as: - - /dev/sg/c1b2t3u4 - - -IDE Hard Discs - -All IDE discs are placed under /dev/ide/hd, using a similar -convention to SCSI discs. The following mappings exist between the new -and the old names: - - /dev/hda /dev/ide/hd/c0b0t0u0 - /dev/hdb /dev/ide/hd/c0b0t1u0 - /dev/hdc /dev/ide/hd/c0b1t0u0 - /dev/hdd /dev/ide/hd/c0b1t1u0 - - -IDE Tapes - -A similar naming scheme is used as for IDE discs. The entries will -appear in the /dev/ide/mt directory. - -IDE CD-ROM - -A similar naming scheme is used as for IDE discs. The entries will -appear in the /dev/ide/cd directory. - -IDE Floppies - -A similar naming scheme is used as for IDE discs. The entries will -appear in the /dev/ide/fd directory. - -XT Hard Discs - -All XT discs are placed under /dev/xd. The first XT disc -would appear as /dev/xd/c0t0. - - -Old Compatibility Names - -The old compatibility names are the legacy device names, such as -/dev/hda, /dev/sda, /dev/rtc and so on. -Devfsd can be configured to create compatibility symlinks so that you -may continue to use the old names in your configuration files and so -that old applications will continue to function correctly. - -In order to configure devfsd to create these legacy names, the -following lines should be placed in your /etc/devfsd.conf: - -REGISTER .* MKOLDCOMPAT -UNREGISTER .* RMOLDCOMPAT - -This will cause devfsd to create (and destroy) symbolic links which -point to the kernel-supplied names. - - ------------------------------------------------------------------------------ - - -Device drivers currently ported - -- All miscellaneous character devices support devfs (this is done - transparently through misc_register()) - -- SCSI discs and generic hard discs - -- Character memory devices (null, zero, full and so on) - Thanks to C. Scott Ananian <cananian@alumni.princeton.edu> - -- Loop devices (/dev/loop?) - -- TTY devices (console, serial ports, terminals and pseudo-terminals) - Thanks to C. Scott Ananian <cananian@alumni.princeton.edu> - -- SCSI tapes (/dev/scsi and /dev/tapes) - -- SCSI CD-ROMs (/dev/scsi and /dev/cdroms) - -- SCSI generic devices (/dev/scsi) - -- RAMDISCS (/dev/ram?) - -- Meta Devices (/dev/md*) - -- Floppy discs (/dev/floppy) - -- Parallel port printers (/dev/printers) - -- Sound devices (/dev/sound) - Thanks to Eric Dumas <dumas@linux.eu.org> and - C. Scott Ananian <cananian@alumni.princeton.edu> - -- Joysticks (/dev/joysticks) - -- Sparc keyboard (/dev/kbd) - -- DSP56001 digital signal processor (/dev/dsp56k) - -- Apple Desktop Bus (/dev/adb) - -- Coda network file system (/dev/cfs*) - -- Virtual console capture devices (/dev/vcc) - Thanks to Dennis Hou <smilax@mindmeld.yi.org> - -- Frame buffer devices (/dev/fb) - -- Video capture devices (/dev/v4l) - - ------------------------------------------------------------------------------ - - -Allocation of Device Numbers - -Devfs allows you to write a driver which doesn't need to allocate a -device number (major&minor numbers) for the internal operation of the -kernel. However, there are a number of userspace programmes that use -the device number as a unique handle for a device. An example is the -find programme, which uses device numbers to determine whether -an inode is on a different filesystem than another inode. The device -number used is the one for the block device which a filesystem is -using. To preserve compatibility with userspace programmes, block -devices using devfs need to have unique device numbers allocated to -them. Furthermore, POSIX specifies device numbers, so some kind of -device number needs to be presented to userspace. - -The simplest option (especially when porting drivers to devfs) is to -keep using the old major and minor numbers. Devfs will take whatever -values are given for major&minor and pass them onto userspace. - -This device number is a 16 bit number, so this leaves plenty of space -for large numbers of discs and partitions. This scheme can also be -used for character devices, in particular the tty devices, which are -currently limited to 256 pseudo-ttys (this limits the total number of -simultaneous xterms and remote logins). Note that the device number -is limited to the range 36864-61439 (majors 144-239), in order to -avoid any possible conflicts with existing official allocations. - -Please note that using dynamically allocated block device numbers may -break the NFS daemons (both user and kernel mode), which expect dev_t -for a given device to be constant over the lifetime of remote mounts. - -A final note on this scheme: since it doesn't increase the size of -device numbers, there are no compatibility issues with userspace. - ------------------------------------------------------------------------------ - - -Questions and Answers - - -Making things work -Alternatives to devfs -What I don't like about devfs -How to report bugs -Strange kernel messages -Compilation problems with devfsd - - - -Making things work - -Here are some common questions and answers. - - - -Devfsd doesn't start - -Make sure you have compiled and installed devfsd -Make sure devfsd is being started from your boot -scripts -Make sure you have configured your kernel to enable devfs (see -below) -Make sure devfs is mounted (see below) - - -Devfsd is not managing all my permissions - -Make sure you are capturing the appropriate events. For example, -device entries created by the kernel generate REGISTER events, -but those created by devfsd generate CREATE events. - - -Devfsd is not capturing all REGISTER events - -See the previous entry: you may need to capture CREATE events. - - -X will not start - -Make sure you followed the steps -outlined above. - - -Why don't my network devices appear in devfs? - -This is not a bug. Network devices have their own, completely separate -namespace. They are accessed via socket(2) and -setsockopt(2) calls, and thus require no device nodes. I have -raised the possibilty of moving network devices into the device -namespace, but have had no response. - - -How can I test if I have devfs compiled into my kernel? - -All filesystems built-in or currently loaded are listed in -/proc/filesystems. If you see a devfs entry, then -you know that devfs was compiled into your kernel. If you have -correctly configured and rebuilt your kernel, then devfs will be -built-in. If you think you've configured it in, but -/proc/filesystems doesn't show it, you've made a mistake. -Common mistakes include: - -Using a 2.2.x kernel without applying the devfs patch (if you -don't know how to patch your kernel, use 2.4.x instead, don't bother -asking me how to patch) -Forgetting to set CONFIG_EXPERIMENTAL=y -Forgetting to set CONFIG_DEVFS_FS=y -Forgetting to set CONFIG_DEVFS_MOUNT=y (if you want devfs -to be automatically mounted at boot) -Editing your .config manually, instead of using make -config or make xconfig -Forgetting to run make dep; make clean after changing the -configuration and before compiling -Forgetting to compile your kernel and modules -Forgetting to install your kernel -Forgetting to install your modules - -Please check twice that you've done all these steps before sending in -a bug report. - - - -How can I test if devfs is mounted on /dev? - -The device filesystem will always create an entry called -".devfsd", which is used to communicate with the daemon. Even -if the daemon is not running, this entry will exist. Testing for the -existence of this entry is the approved method of determining if devfs -is mounted or not. Note that the type of entry (i.e. regular file, -character device, named pipe, etc.) may change without notice. Only -the existence of the entry should be relied upon. - - -When I start devfsd, I see the error: -Error opening file: ".devfsd" No such file or directory? - -This means that devfs is not mounted. Make sure you have devfs mounted. - - -How do I mount devfs? - -First make sure you have devfs compiled into your kernel (see -above). Then you will either need to: - -set CONFIG_DEVFS_MOUNT=y in your kernel config -pass devfs=mount to your boot loader -mount devfs manually in your boot scripts with: -mount -t none devfs /dev - - - -Mount by volume LABEL=<label> doesn't work with -devfs - -Most probably you are not mounting devfs onto /dev. What -happens is that if your kernel config has CONFIG_DEVFS_FS=y -then the contents of /proc/partitions will have the devfs -names (such as scsi/host0/bus0/target0/lun0/part1). The -contents of /proc/partitions are used by mount(8) when -mounting by volume label. If devfs is not mounted on /dev, -then mount(8) will fail to find devices. The solution is to -make sure that devfs is mounted on /dev. See above for how to -do that. - - -I have extra or incorrect entries in /dev - -You may have stale entries in your dev-state area. Check for a -RESTORE configuration line in your devfsd configuration -(typically /etc/devfsd.conf). If you have this line, check -the contents of the specified directory for stale entries. Remove -any entries which are incorrect, then reboot. - - -I get "Unable to open initial console" messages at boot - -This usually happens when you don't have devfs automounted onto -/dev at boot time, and there is no valid -/dev/console entry on your root file-system. Create a valid -/dev/console device node. - - - - - -Alternatives to devfs - -I've attempted to collate all the anti-devfs proposals and explain -their limitations. Under construction. - - -Why not just pass device create/remove events to a daemon? - -Here the suggestion is to develop an API in the kernel so that devices -can register create and remove events, and a daemon listens for those -events. The daemon would then populate/depopulate /dev (which -resides on disc). - -This has several limitations: - - -it only works for modules loaded and unloaded (or devices inserted -and removed) after the kernel has finished booting. Without a database -of events, there is no way the daemon could fully populate -/dev - - -if you add a database to this scheme, the question is then how to -present that database to user-space. If you make it a list of strings -with embedded event codes which are passed through a pipe to the -daemon, then this is only of use to the daemon. I would argue that the -natural way to present this data is via a filesystem (since many of -the events will be of a hierarchical nature), such as devfs. -Presenting the data as a filesystem makes it easy for the user to see -what is available and also makes it easy to write scripts to scan the -"database" - - -the tight binding between device nodes and drivers is no longer -possible (requiring the otherwise perfectly avoidable -table lookups) - - -you cannot catch inode lookup events on /dev which means -that module autoloading requires device nodes to be created. This is a -problem, particularly for drivers where only a few inodes are created -from a potentially large set - - -this technique can't be used when the root FS is mounted -read-only - - - - -Just implement a better scsidev - -This suggestion involves taking the scsidev programme and -extending it to scan for all devices, not just SCSI devices. The -scsidev programme works by scanning /proc/scsi - -Problems: - - -the kernel does not currently provide a list of all devices -available. Not all drivers register entries in /proc or -generate kernel messages - - -there is no uniform mechanism to register devices other than the -devfs API - - -implementing such an API is then the same as the -proposal above - - - - -Put /dev on a ramdisc - -This suggestion involves creating a ramdisc and populating it with -device nodes and then mounting it over /dev. - -Problems: - - - -this doesn't help when mounting the root filesystem, since you -still need a device node to do that - - -if you want to use this technique for the root device node as -well, you need to use initrd. This complicates the booting sequence -and makes it significantly harder to administer and configure. The -initrd is essentially opaque, robbing the system administrator of easy -configuration - - -insufficient information is available to correctly populate the -ramdisc. So we come back to the -proposal above to "solve" this - - -a ramdisc-based solution would take more kernel memory, since the -backing store would be (at best) normal VFS inodes and dentries, which -take 284 bytes and 112 bytes, respectively, for each entry. Compare -that to 72 bytes for devfs - - - - -Do nothing: there's no problem - -Sometimes people can be heard to claim that the existing scheme is -fine. This is what they're ignoring: - - -device number size (8 bits each for major and minor) is a real -limitation, and must be fixed somehow. Systems with large numbers of -SCSI devices, for example, will continue to consume the remaining -unallocated major numbers. USB will also need to push beyond the 8 bit -minor limitation - - -simply increasing the device number size is insufficient. Apart -from causing a lot of pain, it doesn't solve the management issues -of a /dev with thousands or more device nodes - - -ignoring the problem of a huge /dev will not make it go -away, and dismisses the legitimacy of a large number of people who -want a dynamic /dev - - -the standard response then becomes: "write a device management -daemon", which brings us back to the -proposal above - - - - -What I don't like about devfs - -Here are some common complaints about devfs, and some suggestions and -solutions that may make it more palatable for you. I can't please -everybody, but I do try :-) - -I hate the naming scheme - -First, remember that no naming scheme will please everybody. You hate -the scheme, others love it. Who's to say who's right and who's wrong? -Ultimately, the person who writes the code gets to choose, and what -exists now is a combination of the choices made by the -devfs author and the -kernel maintainer (Linus). - -However, not all is lost. If you want to create your own naming -scheme, it is a simple matter to write a standalone script, hack -devfsd, or write a script called by devfsd. You can create whatever -naming scheme you like. - -Further, if you want to remove all traces of the devfs naming scheme -from /dev, you can mount devfs elsewhere (say -/devfs) and populate /dev with links into -/devfs. This population can be automated using devfsd if you -wish. - -You can even use the VFS binding facility to make the links, rather -than using symbolic links. This way, you don't even have to see the -"destination" of these symbolic links. - -Devfs puts policy into the kernel - -There's already policy in the kernel. Device numbers are in fact -policy (why should the kernel dictate what device numbers I use?). -Face it, some policy has to be in the kernel. The real difference -between device names as policy and device numbers as policy is that -no one will use device numbers directly, because device -numbers are devoid of meaning to humans and are ugly. At least with -the devfs device names, (even though you can add your own naming -scheme) some people will use the devfs-supplied names directly. This -offends some people :-) - -Devfs is bloatware - -This is not even remotely true. As shown above, -both code and data size are quite modest. - - -How to report bugs - -If you have (or think you have) a bug with devfs, please follow the -steps below: - - - -make sure you have enabled debugging output when configuring your -kernel. You will need to set (at least) the following config options: - -CONFIG_DEVFS_DEBUG=y -CONFIG_DEBUG_KERNEL=y -CONFIG_DEBUG_SLAB=y - - - -please make sure you have the latest devfs patches applied. The -latest kernel version might not have the latest devfs patches applied -yet (Linus is very busy) - - -save a copy of your complete kernel logs (preferably by -using the dmesg programme) for later inclusion in your bug -report. You may need to use the -s switch to increase the -internal buffer size so you can capture all the boot messages. -Don't edit or trim the dmesg output - - - - -try booting with devfs=dall passed to the kernel boot -command line (read the documentation on your bootloader on how to do -this), and save the result to a file. This may be quite verbose, and -it may overflow the messages buffer, but try to get as much of it as -you can - - -send a copy of your devfsd configuration file(s) - -send the bug report to me first. -Don't expect that I will see it if you post it to the linux-kernel -mailing list. Include all the information listed above, plus -anything else that you think might be relevant. Put the string -devfs somewhere in the subject line, so my mail filters mark -it as urgent - - - - -Here is a general guide on how to ask questions in a way that greatly -improves your chances of getting a reply: - -http://www.tuxedo.org/~esr/faqs/smart-questions.html. If you have -a bug to report, you should also read - -http://www.chiark.greenend.org.uk/~sgtatham/bugs.html. - - -Strange kernel messages - -You may see devfs-related messages in your kernel logs. Below are some -messages and what they mean (and what you should do about them, if -anything). - - - -devfs_register(fred): could not append to parent, err: -17 - -You need to check what the error code means, but usually 17 means -EEXIST. This means that a driver attempted to create an entry -fred in a directory, but there already was an entry with that -name. This is often caused by flawed boot scripts which untar a bunch -of inodes into /dev, as a way to restore permissions. This -message is harmless, as the device nodes will still -provide access to the driver (unless you use the devfs=only -boot option, which is only for dedicated souls:-). If you want to get -rid of these annoying messages, upgrade to devfsd-v1.3.20 and use the -recommended RESTORE directive to restore permissions. - - -devfs_mk_dir(bill): using old entry in dir: c1808724 "" - -This is similar to the message above, except that a driver attempted -to create a directory named bill, and the parent directory -has an entry with the same name. In this case, to ensure that drivers -continue to work properly, the old entry is re-used and given to the -driver. In 2.5 kernels, the driver is given a NULL entry, and thus, -under rare circumstances, may not create the require device nodes. -The solution is the same as above. - - - - - -Compilation problems with devfsd - -Usually, you can compile devfsd just by typing in -make in the source directory, followed by a make -install (as root). Sometimes, you may have problems, particularly -on broken configurations. - - - -error messages relating to DEVFSD_NOTIFY_DELETE - -This happened because you have an ancient set of kernel headers -installed in /usr/include/linux or /usr/src/linux. -Install kernel 2.4.10 or later. You may need to pass the -KERNEL_DIR variable to make (if you did not install -the new kernel sources as /usr/src/linux), or you may copy -the devfs_fs.h file in the kernel source tree into -/usr/include/linux. - - - - ------------------------------------------------------------------------------ - - -Other resources - - - -Douglas Gilbert has written a useful document at - -http://www.torque.net/sg/devfs_scsi.html which -explores the SCSI subsystem and how it interacts with devfs - - -Douglas Gilbert has written another useful document at - -http://www.torque.net/scsi/SCSI-2.4-HOWTO/ which -discusses the Linux SCSI subsystem in 2.4. - - -Johannes Erdfelt has started a discussion paper on Linux and -hot-swap devices, describing what the requirements are for a scalable -solution and how and why he's used devfs+devfsd. Note that this is an -early draft only, available in plain text form at: - -http://johannes.erdfelt.com/hotswap.txt. -Johannes has promised a HTML version will follow. - - -I presented an invited -paper -at the - -2nd Annual Storage Management Workshop held in Miamia, Florida, -U.S.A. in October 2000. - - - - ------------------------------------------------------------------------------ - - -Translations of this document - -This document has been translated into other languages. - - - - -The document master (in English) by rgooch@atnf.csiro.au is -available at - -http://www.atnf.csiro.au/~rgooch/linux/docs/devfs.html - - - -A Korean translation by viatoris@nownuri.net is available at - -http://your.destiny.pe.kr/devfs/devfs.html - - - - ------------------------------------------------------------------------------ -Most flags courtesy of ITA's -Flags of All Countries -used with permission. diff --git a/Documentation/filesystems/devfs/ToDo b/Documentation/filesystems/devfs/ToDo deleted file mode 100644 index afd5a8f..0000000 --- a/Documentation/filesystems/devfs/ToDo +++ /dev/null @@ -1,40 +0,0 @@ - Device File System (devfs) ToDo List - - Richard Gooch <rgooch@atnf.csiro.au> - - 3-JUL-2000 - -This is a list of things to be done for better devfs support in the -Linux kernel. If you'd like to contribute to the devfs, please have a -look at this list for anything that is unallocated. Also, if there are -items missing (surely), please contact me so I can add them to the -list (preferably with your name attached to them:-). - - -- >256 ptys - Thanks to C. Scott Ananian <cananian@alumni.princeton.edu> - -- Amiga floppy driver (drivers/block/amiflop.c) - -- Atari floppy driver (drivers/block/ataflop.c) - -- SWIM3 (Super Woz Integrated Machine 3) floppy driver (drivers/block/swim3.c) - -- Amiga ZorroII ramdisc driver (drivers/block/z2ram.c) - -- Parallel port ATAPI CD-ROM (drivers/block/paride/pcd.c) - -- Parallel port ATAPI floppy (drivers/block/paride/pf.c) - -- AP1000 block driver (drivers/ap1000/ap.c, drivers/ap1000/ddv.c) - -- Archimedes floppy (drivers/acorn/block/fd1772.c) - -- MFM hard drive (drivers/acorn/block/mfmhd.c) - -- I2O block device (drivers/message/i2o/i2o_block.c) - -- ST-RAM device (arch/m68k/atari/stram.c) - -- Raw devices - diff --git a/Documentation/filesystems/devfs/boot-options b/Documentation/filesystems/devfs/boot-options deleted file mode 100644 index df3d33b..0000000 --- a/Documentation/filesystems/devfs/boot-options +++ /dev/null @@ -1,65 +0,0 @@ -/* -*- auto-fill -*- */ - - Device File System (devfs) Boot Options - - Richard Gooch <rgooch@atnf.csiro.au> - - 18-AUG-2001 - - -When CONFIG_DEVFS_DEBUG is enabled, you can pass several boot options -to the kernel to debug devfs. The boot options are prefixed by -"devfs=", and are separated by commas. Spaces are not allowed. The -syntax looks like this: - -devfs=<option1>,<option2>,<option3> - -and so on. For example, if you wanted to turn on debugging for module -load requests and device registration, you would do: - -devfs=dmod,dreg - -You may prefix "no" to any option. This will invert the option. - - -Debugging Options -================= - -These requires CONFIG_DEVFS_DEBUG to be enabled. -Note that all debugging options have 'd' as the first character. By -default all options are off. All debugging output is sent to the -kernel logs. The debugging options do not take effect until the devfs -version message appears (just prior to the root filesystem being -mounted). - -These are the options: - -dmod print module load requests to <request_module> - -dreg print device register requests to <devfs_register> - -dunreg print device unregister requests to <devfs_unregister> - -dchange print device change requests to <devfs_set_flags> - -dilookup print inode lookup requests - -diget print VFS inode allocations - -diunlink print inode unlinks - -dichange print inode changes - -dimknod print calls to mknod(2) - -dall some debugging turned on - - -Other Options -============= - -These control the default behaviour of devfs. The options are: - -mount mount devfs onto /dev at boot time - -only disable non-devfs device nodes for devfs-capable drivers |
