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author | ru <ru@FreeBSD.org> | 2003-06-28 23:53:39 +0000 |
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committer | ru <ru@FreeBSD.org> | 2003-06-28 23:53:39 +0000 |
commit | 348e423dd913fabaea56f15eecca3d155723ee08 (patch) | |
tree | 119cebb3a669617b213ec04fe871163ae082cfb1 /share/man/man4/intro.4 | |
parent | e4f0eb6b17525e227a1bc1d660ab253005530425 (diff) | |
download | FreeBSD-src-348e423dd913fabaea56f15eecca3d155723ee08.zip FreeBSD-src-348e423dd913fabaea56f15eecca3d155723ee08.tar.gz |
Hiten's patchset for section four manpages, slightly edited by me.
Diffstat (limited to 'share/man/man4/intro.4')
-rw-r--r-- | share/man/man4/intro.4 | 41 |
1 files changed, 25 insertions, 16 deletions
diff --git a/share/man/man4/intro.4 b/share/man/man4/intro.4 index 35d3058..67964c8 100644 --- a/share/man/man4/intro.4 +++ b/share/man/man4/intro.4 @@ -37,10 +37,12 @@ and miscellaneous hardware. .Ss The device abstraction Device is a term used mostly for hardware-related stuff that belongs to the system, like disks, printers, or a graphics display with its -keyboard. There are also so-called +keyboard. +There are also so-called .Em pseudo-devices where a device driver emulates the behaviour of a device in software -without any particular underlying hardware. A typical example for +without any particular underlying hardware. +A typical example for the latter class is .Pa /dev/mem , a loophole where the physical memory can be accessed using the regular @@ -48,7 +50,8 @@ file access semantics. .Pp The device abstraction generally provides a common set of system calls layered on top of them, which are dispatched to the corresponding -device driver by the upper layers of the kernel. The set of system +device driver by the upper layers of the kernel. +The set of system calls available for devices is chosen from .Xr open 2 , .Xr close 2 , @@ -79,7 +82,8 @@ Note that this could lead to an inconsistent state, where either there are device nodes that do not have a configured driver associated with them, or there may be drivers that have successfully probed for their devices, but cannot be accessed since the corresponding device node is -still missing. In the first case, any attempt to reference the device +still missing. +In the first case, any attempt to reference the device through the device node will result in an error, returned by the upper layers of the kernel, usually .Er ENXIO . @@ -92,7 +96,8 @@ and .Em character devices, or to use better terms, buffered and unbuffered (raw) -devices. The traditional names are reflected by the letters +devices. +The traditional names are reflected by the letters .Ql b and .Ql c @@ -100,11 +105,13 @@ as the file type identification in the output of .Ql ls -l . Buffered devices are being accessed through the buffer cache of the operating system, and they are solely intended to layer a file system -on top of them. They are normally implemented for disks and disk-like +on top of them. +They are normally implemented for disks and disk-like devices only and, for historical reasons, for tape devices. .Pp Raw devices are available for all drivers, including those that also -implement a buffered device. For the latter group of devices, the +implement a buffered device. +For the latter group of devices, the differentiation is conventionally done by prepending the letter .Ql r to the path name of the device node, for example @@ -115,7 +122,8 @@ is the corresponding device node for the buffered device. .Pp Unbuffered devices should be used for all actions that are not related to file system operations, even if the device in question is a disk -device. This includes making backups of entire disk partitions, or +device. +This includes making backups of entire disk partitions, or to .Em raw floppy disks @@ -126,7 +134,8 @@ file permissions of the device node entry, instead of being enforced directly by the drivers in the kernel. .Ss Drivers without device nodes Drivers for network devices do not use device nodes in order to be -accessed. Their selection is based on other decisions inside the +accessed. +Their selection is based on other decisions inside the kernel, and instead of calling .Xr open 2 , use of a network device is generally introduced by using the system @@ -135,10 +144,11 @@ call .Ss Configuring a driver into the kernel For each kernel, there is a configuration file that is used as a base to select the facilities and drivers for that kernel, and to tune -several options. See +several options. +See .Xr config 8 -for a detailed description of the files involved. The individual -manual pages in this section provide a sample line for the +for a detailed description of the files involved. +The individual manual pages in this section provide a sample line for the configuration file in their synopsis portion. See also the sample config file .Pa /sys/i386/conf/LINT @@ -157,13 +167,12 @@ architecture). .Xr devfs 5 , .Xr hier 7 , .Xr config 8 +.Sh HISTORY +This manual page first appeared in +.Fx 2.1 . .Sh AUTHORS .An -nosplit This man page has been written by .An J\(:org Wunsch with initial input by .An David E. O'Brien . -.Sh HISTORY -.Nm Intro -appeared in -.Fx 2.1 . |