linux/Documentation/ABI
Linus Torvalds 1f0a53f623 LED updates for 4.10 merge cycle.
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Merge tag 'leds_for_4.10' of git://git.kernel.org/pub/scm/linux/kernel/git/j.anaszewski/linux-leds

Pull LED updates from Jacek Anaszewski:

 - userspace LED class driver - it can be useful for testing triggers
   and can also be used to implement virtual LEDs

 - LED class driver for NIC78bx device

 - LED core fixes for preventing potential races while setting
   brightness when software blinking is enabled

 - improvements in LED documentation to mention semantics on changing
   brightness while trigger is active

* tag 'leds_for_4.10' of git://git.kernel.org/pub/scm/linux/kernel/git/j.anaszewski/linux-leds:
  leds: pca955x: Add ACPI support
  leds: netxbig: fix module autoload for OF registration
  leds: pca963x: Add ACPI support
  leds: leds-cobalt-raq: use builtin_platform_driver
  led: core: Fix blink_brightness setting race
  led: core: Use atomic bit-field for the blink-flags
  leds: Add user LED driver for NIC78bx device
  leds: verify vendor and change license in mlxcpld driver
  leds: pca963x: enable low-power state
  leds: pca9532: Use default trigger value from platform data
  leds: pca963x: workaround group blink scaling issue
  cleanup LED documentation and make it match reality
  leds: lp3952: Export I2C module alias information for module autoload
  leds: mc13783: Fix MC13892 keypad led access
  ledtrig-cpu.c: fix english
  leds/leds-lp5523.txt: make documentation match reality
  tools/leds: Add uledmon program for monitoring userspace LEDs
  leds: Use macro for max device node name size
  leds: Introduce userspace LED class driver
  mfd: qcom-pm8xxx: Clean up PM8XXX namespace
2016-12-13 08:01:19 -08:00
..
obsolete Documentation: fix common spelling mistakes 2016-04-28 07:51:59 -06:00
removed rfkill: Remove obsolete "claim" sysfs interface 2016-02-24 09:04:24 +01:00
stable documentation: drivers/core/of: fix name of of_node symlink 2016-08-31 15:14:44 +02:00
testing LED updates for 4.10 merge cycle. 2016-12-13 08:01:19 -08:00
README docs: fix locations of several documents that got moved 2016-10-24 08:12:35 -02:00

This directory attempts to document the ABI between the Linux kernel and
userspace, and the relative stability of these interfaces.  Due to the
everchanging nature of Linux, and the differing maturity levels, these
interfaces should be used by userspace programs in different ways.

We have four different levels of ABI stability, as shown by the four
different subdirectories in this location.  Interfaces may change levels
of stability according to the rules described below.

The different levels of stability are:

  stable/
	This directory documents the interfaces that the developer has
	defined to be stable.  Userspace programs are free to use these
	interfaces with no restrictions, and backward compatibility for
	them will be guaranteed for at least 2 years.  Most interfaces
	(like syscalls) are expected to never change and always be
	available.

  testing/
	This directory documents interfaces that are felt to be stable,
	as the main development of this interface has been completed.
	The interface can be changed to add new features, but the
	current interface will not break by doing this, unless grave
	errors or security problems are found in them.  Userspace
	programs can start to rely on these interfaces, but they must be
	aware of changes that can occur before these interfaces move to
	be marked stable.  Programs that use these interfaces are
	strongly encouraged to add their name to the description of
	these interfaces, so that the kernel developers can easily
	notify them if any changes occur (see the description of the
	layout of the files below for details on how to do this.)

  obsolete/
  	This directory documents interfaces that are still remaining in
	the kernel, but are marked to be removed at some later point in
	time.  The description of the interface will document the reason
	why it is obsolete and when it can be expected to be removed.

  removed/
	This directory contains a list of the old interfaces that have
	been removed from the kernel.

Every file in these directories will contain the following information:

What:		Short description of the interface
Date:		Date created
KernelVersion:	Kernel version this feature first showed up in.
Contact:	Primary contact for this interface (may be a mailing list)
Description:	Long description of the interface and how to use it.
Users:		All users of this interface who wish to be notified when
		it changes.  This is very important for interfaces in
		the "testing" stage, so that kernel developers can work
		with userspace developers to ensure that things do not
		break in ways that are unacceptable.  It is also
		important to get feedback for these interfaces to make
		sure they are working in a proper way and do not need to
		be changed further.


How things move between levels:

Interfaces in stable may move to obsolete, as long as the proper
notification is given.

Interfaces may be removed from obsolete and the kernel as long as the
documented amount of time has gone by.

Interfaces in the testing state can move to the stable state when the
developers feel they are finished.  They cannot be removed from the
kernel tree without going through the obsolete state first.

It's up to the developer to place their interfaces in the category they
wish for it to start out in.


Notable bits of non-ABI, which should not under any circumstances be considered
stable:

- Kconfig.  Userspace should not rely on the presence or absence of any
  particular Kconfig symbol, in /proc/config.gz, in the copy of .config
  commonly installed to /boot, or in any invocation of the kernel build
  process.

- Kernel-internal symbols.  Do not rely on the presence, absence, location, or
  type of any kernel symbol, either in System.map files or the kernel binary
  itself.  See Documentation/process/stable-api-nonsense.rst.