diff options
Diffstat (limited to 'Documentation/DocBook')
| -rw-r--r-- | Documentation/DocBook/gadget.tmpl | 38 | ||||
| -rw-r--r-- | Documentation/DocBook/kernel-locking.tmpl | 82 | ||||
| -rw-r--r-- | Documentation/DocBook/kgdb.tmpl | 28 | ||||
| -rw-r--r-- | Documentation/DocBook/procfs-guide.tmpl | 4 | ||||
| -rw-r--r-- | Documentation/DocBook/uio-howto.tmpl | 63 |
5 files changed, 151 insertions, 64 deletions
diff --git a/Documentation/DocBook/gadget.tmpl b/Documentation/DocBook/gadget.tmpl index 5a8ffa7..ea3bc95 100644 --- a/Documentation/DocBook/gadget.tmpl +++ b/Documentation/DocBook/gadget.tmpl @@ -524,6 +524,44 @@ These utilities include endpoint autoconfiguration. <!-- !Edrivers/usb/gadget/epautoconf.c --> </sect1> +<sect1 id="composite"><title>Composite Device Framework</title> + +<para>The core API is sufficient for writing drivers for composite +USB devices (with more than one function in a given configuration), +and also multi-configuration devices (also more than one function, +but not necessarily sharing a given configuration). +There is however an optional framework which makes it easier to +reuse and combine functions. +</para> + +<para>Devices using this framework provide a <emphasis>struct +usb_composite_driver</emphasis>, which in turn provides one or +more <emphasis>struct usb_configuration</emphasis> instances. +Each such configuration includes at least one +<emphasis>struct usb_function</emphasis>, which packages a user +visible role such as "network link" or "mass storage device". +Management functions may also exist, such as "Device Firmware +Upgrade". +</para> + +!Iinclude/linux/usb/composite.h +!Edrivers/usb/gadget/composite.c + +</sect1> + +<sect1 id="functions"><title>Composite Device Functions</title> + +<para>At this writing, a few of the current gadget drivers have +been converted to this framework. +Near-term plans include converting all of them, except for "gadgetfs". +</para> + +!Edrivers/usb/gadget/f_acm.c +!Edrivers/usb/gadget/f_serial.c + +</sect1> + + </chapter> <chapter id="controllers"><title>Peripheral Controller Drivers</title> diff --git a/Documentation/DocBook/kernel-locking.tmpl b/Documentation/DocBook/kernel-locking.tmpl index 77c42f4..084f6ad 100644 --- a/Documentation/DocBook/kernel-locking.tmpl +++ b/Documentation/DocBook/kernel-locking.tmpl @@ -219,10 +219,10 @@ </para> <sect1 id="lock-intro"> - <title>Three Main Types of Kernel Locks: Spinlocks, Mutexes and Semaphores</title> + <title>Two Main Types of Kernel Locks: Spinlocks and Mutexes</title> <para> - There are three main types of kernel locks. The fundamental type + There are two main types of kernel locks. The fundamental type is the spinlock (<filename class="headerfile">include/asm/spinlock.h</filename>), which is a very simple single-holder lock: if you can't get the @@ -240,14 +240,6 @@ use a spinlock instead. </para> <para> - The third type is a semaphore - (<filename class="headerfile">include/linux/semaphore.h</filename>): it - can have more than one holder at any time (the number decided at - initialization time), although it is most commonly used as a - single-holder lock (a mutex). If you can't get a semaphore, your - task will be suspended and later on woken up - just like for mutexes. - </para> - <para> Neither type of lock is recursive: see <xref linkend="deadlock"/>. </para> @@ -278,7 +270,7 @@ </para> <para> - Semaphores still exist, because they are required for + Mutexes still exist, because they are required for synchronization between <firstterm linkend="gloss-usercontext">user contexts</firstterm>, as we will see below. </para> @@ -289,18 +281,17 @@ <para> If you have a data structure which is only ever accessed from - user context, then you can use a simple semaphore - (<filename>linux/linux/semaphore.h</filename>) to protect it. This - is the most trivial case: you initialize the semaphore to the number - of resources available (usually 1), and call - <function>down_interruptible()</function> to grab the semaphore, and - <function>up()</function> to release it. There is also a - <function>down()</function>, which should be avoided, because it + user context, then you can use a simple mutex + (<filename>include/linux/mutex.h</filename>) to protect it. This + is the most trivial case: you initialize the mutex. Then you can + call <function>mutex_lock_interruptible()</function> to grab the mutex, + and <function>mutex_unlock()</function> to release it. There is also a + <function>mutex_lock()</function>, which should be avoided, because it will not return if a signal is received. </para> <para> - Example: <filename>linux/net/core/netfilter.c</filename> allows + Example: <filename>net/netfilter/nf_sockopt.c</filename> allows registration of new <function>setsockopt()</function> and <function>getsockopt()</function> calls, with <function>nf_register_sockopt()</function>. Registration and @@ -515,7 +506,7 @@ <listitem> <para> If you are in a process context (any syscall) and want to - lock other process out, use a semaphore. You can take a semaphore + lock other process out, use a mutex. You can take a mutex and sleep (<function>copy_from_user*(</function> or <function>kmalloc(x,GFP_KERNEL)</function>). </para> @@ -662,7 +653,7 @@ <entry>SLBH</entry> <entry>SLBH</entry> <entry>SLBH</entry> -<entry>DI</entry> +<entry>MLI</entry> <entry>None</entry> </row> @@ -692,8 +683,8 @@ <entry>spin_lock_bh</entry> </row> <row> -<entry>DI</entry> -<entry>down_interruptible</entry> +<entry>MLI</entry> +<entry>mutex_lock_interruptible</entry> </row> </tbody> @@ -703,6 +694,31 @@ </sect1> </chapter> +<chapter id="trylock-functions"> + <title>The trylock Functions</title> + <para> + There are functions that try to acquire a lock only once and immediately + return a value telling about success or failure to acquire the lock. + They can be used if you need no access to the data protected with the lock + when some other thread is holding the lock. You should acquire the lock + later if you then need access to the data protected with the lock. + </para> + + <para> + <function>spin_trylock()</function> does not spin but returns non-zero if + it acquires the spinlock on the first try or 0 if not. This function can + be used in all contexts like <function>spin_lock</function>: you must have + disabled the contexts that might interrupt you and acquire the spin lock. + </para> + + <para> + <function>mutex_trylock()</function> does not suspend your task + but returns non-zero if it could lock the mutex on the first try + or 0 if not. This function cannot be safely used in hardware or software + interrupt contexts despite not sleeping. + </para> +</chapter> + <chapter id="Examples"> <title>Common Examples</title> <para> @@ -1285,7 +1301,7 @@ as Alan Cox says, <quote>Lock data, not code</quote>. <para> There is a coding bug where a piece of code tries to grab a spinlock twice: it will spin forever, waiting for the lock to - be released (spinlocks, rwlocks and semaphores are not + be released (spinlocks, rwlocks and mutexes are not recursive in Linux). This is trivial to diagnose: not a stay-up-five-nights-talk-to-fluffy-code-bunnies kind of problem. @@ -1310,7 +1326,7 @@ as Alan Cox says, <quote>Lock data, not code</quote>. <para> This complete lockup is easy to diagnose: on SMP boxes the - watchdog timer or compiling with <symbol>DEBUG_SPINLOCKS</symbol> set + watchdog timer or compiling with <symbol>DEBUG_SPINLOCK</symbol> set (<filename>include/linux/spinlock.h</filename>) will show this up immediately when it happens. </para> @@ -1533,7 +1549,7 @@ the amount of locking which needs to be done. <title>Read/Write Lock Variants</title> <para> - Both spinlocks and semaphores have read/write variants: + Both spinlocks and mutexes have read/write variants: <type>rwlock_t</type> and <structname>struct rw_semaphore</structname>. These divide users into two classes: the readers and the writers. If you are only reading the data, you can get a read lock, but to write to @@ -1656,7 +1672,7 @@ the amount of locking which needs to be done. #include <linux/slab.h> #include <linux/string.h> +#include <linux/rcupdate.h> - #include <linux/semaphore.h> + #include <linux/mutex.h> #include <asm/errno.h> struct object @@ -1888,7 +1904,7 @@ machines due to caching. </listitem> <listitem> <para> - <function> put_user()</function> + <function>put_user()</function> </para> </listitem> </itemizedlist> @@ -1902,13 +1918,13 @@ machines due to caching. <listitem> <para> - <function>down_interruptible()</function> and - <function>down()</function> + <function>mutex_lock_interruptible()</function> and + <function>mutex_lock()</function> </para> <para> - There is a <function>down_trylock()</function> which can be + There is a <function>mutex_trylock()</function> which can be used inside interrupt context, as it will not sleep. - <function>up()</function> will also never sleep. + <function>mutex_unlock()</function> will also never sleep. </para> </listitem> </itemizedlist> @@ -1998,7 +2014,7 @@ machines due to caching. <para> Prior to 2.5, or when <symbol>CONFIG_PREEMPT</symbol> is unset, processes in user context inside the kernel would not - preempt each other (ie. you had that CPU until you have it up, + preempt each other (ie. you had that CPU until you gave it up, except for interrupts). With the addition of <symbol>CONFIG_PREEMPT</symbol> in 2.5.4, this changed: when in user context, higher priority tasks can "cut in": spinlocks diff --git a/Documentation/DocBook/kgdb.tmpl b/Documentation/DocBook/kgdb.tmpl index 97618be..e8acd1f 100644 --- a/Documentation/DocBook/kgdb.tmpl +++ b/Documentation/DocBook/kgdb.tmpl @@ -72,7 +72,7 @@ kgdb is a source level debugger for linux kernel. It is used along with gdb to debug a linux kernel. The expectation is that gdb can be used to "break in" to the kernel to inspect memory, variables - and look through a cal stack information similar to what an + and look through call stack information similar to what an application developer would use gdb for. It is possible to place breakpoints in kernel code and perform some limited execution stepping. @@ -84,17 +84,18 @@ runs an instance of gdb against the vmlinux file which contains the symbols (not boot image such as bzImage, zImage, uImage...). In gdb the developer specifies the connection parameters and - connects to kgdb. Depending on which kgdb I/O modules exist in - the kernel for a given architecture, it may be possible to debug - the test machine's kernel with the development machine using a - rs232 or ethernet connection. + connects to kgdb. The type of connection a developer makes with + gdb depends on the availability of kgdb I/O modules compiled as + builtin's or kernel modules in the test machine's kernel. </para> </chapter> <chapter id="CompilingAKernel"> <title>Compiling a kernel</title> <para> - To enable <symbol>CONFIG_KGDB</symbol>, look under the "Kernel debugging" - and then select "KGDB: kernel debugging with remote gdb". + To enable <symbol>CONFIG_KGDB</symbol> you should first turn on + "Prompt for development and/or incomplete code/drivers" + (CONFIG_EXPERIMENTAL) in "General setup", then under the + "Kernel debugging" select "KGDB: kernel debugging with remote gdb". </para> <para> Next you should choose one of more I/O drivers to interconnect debugging @@ -221,7 +222,7 @@ </para> <para> IMPORTANT NOTE: Using this option with kgdb over the console - (kgdboc) or kgdb over ethernet (kgdboe) is not supported. + (kgdboc) is not supported. </para> </sect1> </chapter> @@ -247,18 +248,11 @@ (gdb) target remote /dev/ttyS0 </programlisting> <para> - Example (kgdb to a terminal server): + Example (kgdb to a terminal server on tcp port 2012): </para> <programlisting> % gdb ./vmlinux - (gdb) target remote udp:192.168.2.2:6443 - </programlisting> - <para> - Example (kgdb over ethernet): - </para> - <programlisting> - % gdb ./vmlinux - (gdb) target remote udp:192.168.2.2:6443 + (gdb) target remote 192.168.2.2:2012 </programlisting> <para> Once connected, you can debug a kernel the way you would debug an diff --git a/Documentation/DocBook/procfs-guide.tmpl b/Documentation/DocBook/procfs-guide.tmpl index 1fd6a1e..8a5dc6e 100644 --- a/Documentation/DocBook/procfs-guide.tmpl +++ b/Documentation/DocBook/procfs-guide.tmpl @@ -29,12 +29,12 @@ <revhistory> <revision> - <revnumber>1.0 </revnumber> + <revnumber>1.0</revnumber> <date>May 30, 2001</date> <revremark>Initial revision posted to linux-kernel</revremark> </revision> <revision> - <revnumber>1.1 </revnumber> + <revnumber>1.1</revnumber> <date>June 3, 2001</date> <revremark>Revised after comments from linux-kernel</revremark> </revision> diff --git a/Documentation/DocBook/uio-howto.tmpl b/Documentation/DocBook/uio-howto.tmpl index fdd7f4f..df87d1b 100644 --- a/Documentation/DocBook/uio-howto.tmpl +++ b/Documentation/DocBook/uio-howto.tmpl @@ -21,6 +21,18 @@ </affiliation> </author> +<copyright> + <year>2006-2008</year> + <holder>Hans-Jürgen Koch.</holder> +</copyright> + +<legalnotice> +<para> +This documentation is Free Software licensed under the terms of the +GPL version 2. +</para> +</legalnotice> + <pubdate>2006-12-11</pubdate> <abstract> @@ -30,6 +42,12 @@ <revhistory> <revision> + <revnumber>0.5</revnumber> + <date>2008-05-22</date> + <authorinitials>hjk</authorinitials> + <revremark>Added description of write() function.</revremark> + </revision> + <revision> <revnumber>0.4</revnumber> <date>2007-11-26</date> <authorinitials>hjk</authorinitials> @@ -57,20 +75,9 @@ </bookinfo> <chapter id="aboutthisdoc"> -<?dbhtml filename="about.html"?> +<?dbhtml filename="aboutthis.html"?> <title>About this document</title> -<sect1 id="copyright"> -<?dbhtml filename="copyright.html"?> -<title>Copyright and License</title> -<para> - Copyright (c) 2006 by Hans-Jürgen Koch.</para> -<para> -This documentation is Free Software licensed under the terms of the -GPL version 2. -</para> -</sect1> - <sect1 id="translations"> <?dbhtml filename="translations.html"?> <title>Translations</title> @@ -189,6 +196,30 @@ interested in translating it, please email me represents the total interrupt count. You can use this number to figure out if you missed some interrupts. </para> + <para> + For some hardware that has more than one interrupt source internally, + but not separate IRQ mask and status registers, there might be + situations where userspace cannot determine what the interrupt source + was if the kernel handler disables them by writing to the chip's IRQ + register. In such a case, the kernel has to disable the IRQ completely + to leave the chip's register untouched. Now the userspace part can + determine the cause of the interrupt, but it cannot re-enable + interrupts. Another cornercase is chips where re-enabling interrupts + is a read-modify-write operation to a combined IRQ status/acknowledge + register. This would be racy if a new interrupt occurred + simultaneously. + </para> + <para> + To address these problems, UIO also implements a write() function. It + is normally not used and can be ignored for hardware that has only a + single interrupt source or has separate IRQ mask and status registers. + If you need it, however, a write to <filename>/dev/uioX</filename> + will call the <function>irqcontrol()</function> function implemented + by the driver. You have to write a 32-bit value that is usually either + 0 or 1 to disable or enable interrupts. If a driver does not implement + <function>irqcontrol()</function>, <function>write()</function> will + return with <varname>-ENOSYS</varname>. + </para> <para> To handle interrupts properly, your custom kernel module can @@ -362,6 +393,14 @@ device is actually used. <function>open()</function>, you will probably also want a custom <function>release()</function> function. </para></listitem> + +<listitem><para> +<varname>int (*irqcontrol)(struct uio_info *info, s32 irq_on) +</varname>: Optional. If you need to be able to enable or disable +interrupts from userspace by writing to <filename>/dev/uioX</filename>, +you can implement this function. The parameter <varname>irq_on</varname> +will be 0 to disable interrupts and 1 to enable them. +</para></listitem> </itemizedlist> <para> |
