linux/Documentation/core-api/kernel-api.rst
Linus Torvalds b1cce98493 It has been a relatively busy cycle for docs, especially the build system:
- The Perl kernel-doc script was added to 2.3.52pre1 just after the turn of
   the millennium.  Over the following 25 years, it accumulated a vast
   amount of cruft, all in a language few people want to deal with anymore.
   Mauro's Python replacement in 6.16 faithfully reproduced all of the cruft
   in the hope of avoiding regressions.  Now that we have a more reasonable
   code base, though, we can work on cleaning it up; many of the changes
   this time around are toward that end.
 
 - A reorganization of the ext4 docs into the usual TOC format.
 
 - Various Chinese translations and updates.
 
 - A new script from Mauro to help with docs-build testing.
 
 - A new document for linked lists
 
 - A sweep through MAINTAINERS fixing broken GitHub git:// repository links.
 
 ...and lots of fixes and updates.
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Merge tag 'docs-6.17' of git://git.lwn.net/linux

Pull documentation updates from Jonathan Corbet:
 "It has been a relatively busy cycle for docs, especially the build
  system:

   - The Perl kernel-doc script was added to 2.3.52pre1 just after the
     turn of the millennium. Over the following 25 years, it accumulated
     a vast amount of cruft, all in a language few people want to deal
     with anymore. Mauro's Python replacement in 6.16 faithfully
     reproduced all of the cruft in the hope of avoiding regressions.

     Now that we have a more reasonable code base, though, we can work
     on cleaning it up; many of the changes this time around are toward
     that end.

   - A reorganization of the ext4 docs into the usual TOC format.

   - Various Chinese translations and updates.

   - A new script from Mauro to help with docs-build testing.

   - A new document for linked lists

   - A sweep through MAINTAINERS fixing broken GitHub git:// repository
     links.

  ...and lots of fixes and updates"

* tag 'docs-6.17' of git://git.lwn.net/linux: (147 commits)
  scripts: add origin commit identification based on specific patterns
  sphinx: kernel_abi: fix performance regression with O=<dir>
  Documentation: core-api: entry: Replace deprecated KVM entry/exit functions
  docs: fault-injection: drop reference to md-faulty
  docs: document linked lists
  scripts: kdoc: make it backward-compatible with Python 3.7
  docs: kernel-doc: emit warnings for ancient versions of Python
  Documentation/rtla: Describe exit status
  Documentation/rtla: Add include common_appendix.rst
  docs: kernel: Clarify printk_ratelimit_burst reset behavior
  Documentation: ioctl-number: Don't repeat macro names
  Documentation: ioctl-number: Shorten macros table
  Documentation: ioctl-number: Correct full path to papr-physical-attestation.h
  Documentation: ioctl-number: Extend "Include File" column width
  Documentation: ioctl-number: Fix linuxppc-dev mailto link
  overlayfs.rst: fix typos
  docs: kdoc: emit a warning for ancient versions of Python
  docs: kdoc: clean up check_sections()
  docs: kdoc: directly access the always-there KdocItem fields
  docs: kdoc: straighten up dump_declaration()
  ...
2025-07-31 08:36:51 -07:00

430 lines
8.9 KiB
ReStructuredText

====================
The Linux Kernel API
====================
Basic C Library Functions
=========================
When writing drivers, you cannot in general use routines which are from
the C Library. Some of the functions have been found generally useful
and they are listed below. The behaviour of these functions may vary
slightly from those defined by ANSI, and these deviations are noted in
the text.
String Conversions
------------------
.. kernel-doc:: lib/vsprintf.c
:export:
.. kernel-doc:: include/linux/kstrtox.h
:functions: kstrtol kstrtoul
.. kernel-doc:: lib/kstrtox.c
:export:
.. kernel-doc:: lib/string_helpers.c
:export:
String Manipulation
-------------------
.. kernel-doc:: include/linux/fortify-string.h
:internal:
.. kernel-doc:: lib/string.c
:export:
.. kernel-doc:: include/linux/string.h
:internal:
.. kernel-doc:: mm/util.c
:functions: kstrdup kstrdup_const kstrndup kmemdup kmemdup_nul memdup_user
vmemdup_user strndup_user memdup_user_nul
Basic Kernel Library Functions
==============================
The Linux kernel provides more basic utility functions.
Bit Operations
--------------
.. kernel-doc:: include/asm-generic/bitops/instrumented-atomic.h
:internal:
.. kernel-doc:: include/asm-generic/bitops/instrumented-non-atomic.h
:internal:
.. kernel-doc:: include/asm-generic/bitops/instrumented-lock.h
:internal:
Bitmap Operations
-----------------
.. kernel-doc:: lib/bitmap.c
:doc: bitmap introduction
.. kernel-doc:: include/linux/bitmap.h
:doc: declare bitmap
.. kernel-doc:: include/linux/bitmap.h
:doc: bitmap overview
.. kernel-doc:: include/linux/bitmap.h
:doc: bitmap bitops
.. kernel-doc:: lib/bitmap.c
:export:
.. kernel-doc:: lib/bitmap.c
:internal:
.. kernel-doc:: include/linux/bitmap.h
:internal:
Command-line Parsing
--------------------
.. kernel-doc:: lib/cmdline.c
:export:
Error Pointers
--------------
.. kernel-doc:: include/linux/err.h
:internal:
Sorting
-------
.. kernel-doc:: lib/sort.c
:export:
.. kernel-doc:: lib/list_sort.c
:export:
Text Searching
--------------
.. kernel-doc:: lib/textsearch.c
:doc: ts_intro
.. kernel-doc:: lib/textsearch.c
:export:
.. kernel-doc:: include/linux/textsearch.h
:functions: textsearch_find textsearch_next \
textsearch_get_pattern textsearch_get_pattern_len
CRC and Math Functions in Linux
===============================
Arithmetic Overflow Checking
----------------------------
.. kernel-doc:: include/linux/overflow.h
:internal:
CRC Functions
-------------
.. kernel-doc:: lib/crc/crc4.c
:export:
.. kernel-doc:: lib/crc/crc7.c
:export:
.. kernel-doc:: lib/crc/crc8.c
:export:
.. kernel-doc:: lib/crc/crc16.c
:export:
.. kernel-doc:: lib/crc/crc-ccitt.c
:export:
.. kernel-doc:: lib/crc/crc-itu-t.c
:export:
.. kernel-doc:: include/linux/crc32.h
.. kernel-doc:: include/linux/crc64.h
Base 2 log and power Functions
------------------------------
.. kernel-doc:: include/linux/log2.h
:internal:
Integer log and power Functions
-------------------------------
.. kernel-doc:: include/linux/int_log.h
.. kernel-doc:: lib/math/int_pow.c
:export:
.. kernel-doc:: lib/math/int_sqrt.c
:export:
Division Functions
------------------
.. kernel-doc:: include/asm-generic/div64.h
:functions: do_div
.. kernel-doc:: include/linux/math64.h
:internal:
.. kernel-doc:: lib/math/gcd.c
:export:
UUID/GUID
---------
.. kernel-doc:: lib/uuid.c
:export:
Kernel IPC facilities
=====================
IPC utilities
-------------
.. kernel-doc:: ipc/util.c
:internal:
FIFO Buffer
===========
kfifo interface
---------------
.. kernel-doc:: include/linux/kfifo.h
:internal:
relay interface support
=======================
Relay interface support is designed to provide an efficient mechanism
for tools and facilities to relay large amounts of data from kernel
space to user space.
relay interface
---------------
.. kernel-doc:: kernel/relay.c
:export:
.. kernel-doc:: kernel/relay.c
:internal:
Module Support
==============
Kernel module auto-loading
--------------------------
.. kernel-doc:: kernel/module/kmod.c
:export:
Module debugging
----------------
.. kernel-doc:: kernel/module/stats.c
:doc: module debugging statistics overview
dup_failed_modules - tracks duplicate failed modules
****************************************************
.. kernel-doc:: kernel/module/stats.c
:doc: dup_failed_modules - tracks duplicate failed modules
module statistics debugfs counters
**********************************
.. kernel-doc:: kernel/module/stats.c
:doc: module statistics debugfs counters
Inter Module support
--------------------
Refer to the files in kernel/module/ for more information.
Hardware Interfaces
===================
DMA Channels
------------
.. kernel-doc:: kernel/dma.c
:export:
Resources Management
--------------------
.. kernel-doc:: kernel/resource.c
:internal:
.. kernel-doc:: kernel/resource.c
:export:
MTRR Handling
-------------
.. kernel-doc:: arch/x86/kernel/cpu/mtrr/mtrr.c
:export:
Security Framework
==================
.. kernel-doc:: security/security.c
:internal:
.. kernel-doc:: security/inode.c
:export:
Audit Interfaces
================
.. kernel-doc:: kernel/audit.c
:export:
.. kernel-doc:: kernel/auditsc.c
:internal:
.. kernel-doc:: kernel/auditfilter.c
:internal:
Accounting Framework
====================
.. kernel-doc:: kernel/acct.c
:internal:
Block Devices
=============
.. kernel-doc:: include/linux/bio.h
.. kernel-doc:: block/blk-core.c
:export:
.. kernel-doc:: block/blk-core.c
:internal:
.. kernel-doc:: block/blk-map.c
:export:
.. kernel-doc:: block/blk-sysfs.c
:internal:
.. kernel-doc:: block/blk-settings.c
:export:
.. kernel-doc:: block/blk-flush.c
:export:
.. kernel-doc:: block/blk-lib.c
:export:
.. kernel-doc:: block/blk-integrity.c
:export:
.. kernel-doc:: kernel/trace/blktrace.c
:internal:
.. kernel-doc:: block/genhd.c
:internal:
.. kernel-doc:: block/genhd.c
:export:
.. kernel-doc:: block/bdev.c
:export:
Char devices
============
.. kernel-doc:: fs/char_dev.c
:export:
Clock Framework
===============
The clock framework defines programming interfaces to support software
management of the system clock tree. This framework is widely used with
System-On-Chip (SOC) platforms to support power management and various
devices which may need custom clock rates. Note that these "clocks"
don't relate to timekeeping or real time clocks (RTCs), each of which
have separate frameworks. These :c:type:`struct clk <clk>`
instances may be used to manage for example a 96 MHz signal that is used
to shift bits into and out of peripherals or busses, or otherwise
trigger synchronous state machine transitions in system hardware.
Power management is supported by explicit software clock gating: unused
clocks are disabled, so the system doesn't waste power changing the
state of transistors that aren't in active use. On some systems this may
be backed by hardware clock gating, where clocks are gated without being
disabled in software. Sections of chips that are powered but not clocked
may be able to retain their last state. This low power state is often
called a *retention mode*. This mode still incurs leakage currents,
especially with finer circuit geometries, but for CMOS circuits power is
mostly used by clocked state changes.
Power-aware drivers only enable their clocks when the device they manage
is in active use. Also, system sleep states often differ according to
which clock domains are active: while a "standby" state may allow wakeup
from several active domains, a "mem" (suspend-to-RAM) state may require
a more wholesale shutdown of clocks derived from higher speed PLLs and
oscillators, limiting the number of possible wakeup event sources. A
driver's suspend method may need to be aware of system-specific clock
constraints on the target sleep state.
Some platforms support programmable clock generators. These can be used
by external chips of various kinds, such as other CPUs, multimedia
codecs, and devices with strict requirements for interface clocking.
.. kernel-doc:: include/linux/clk.h
:internal:
Synchronization Primitives
==========================
Read-Copy Update (RCU)
----------------------
.. kernel-doc:: include/linux/rcupdate.h
.. kernel-doc:: kernel/rcu/tree.c
.. kernel-doc:: kernel/rcu/tree_exp.h
.. kernel-doc:: kernel/rcu/update.c
.. kernel-doc:: include/linux/srcu.h
.. kernel-doc:: kernel/rcu/srcutree.c
.. kernel-doc:: include/linux/rculist_bl.h
.. kernel-doc:: include/linux/rculist.h
.. kernel-doc:: include/linux/rculist_nulls.h
.. kernel-doc:: include/linux/rcu_sync.h
.. kernel-doc:: kernel/rcu/sync.c
.. kernel-doc:: kernel/rcu/tasks.h
.. kernel-doc:: kernel/rcu/tree_stall.h
.. kernel-doc:: include/linux/rcupdate_trace.h
.. kernel-doc:: include/linux/rcupdate_wait.h
.. kernel-doc:: include/linux/rcuref.h
.. kernel-doc:: include/linux/rcutree.h