linux/Documentation/ABI
Linus Torvalds 2be6bc48df - Core Frameworks
- Add new framework to support Group Multi-Color (GMC) LEDs
    - Offer an 'optional' API for non-essential LEDs
    - Support obtaining 'max brightness' values from Device Tree
    - Provide new led_classdev member 'color' (settable via DT and SYFS)
    - Stop TTY Trigger from using the old LED_ON constraints
    - Statically allocate leds_class
 
  - New Drivers
    - Add support for NXP PCA995x I2C Constant Current LED Driver
 
  - New Device Support
    - Add support for Siemens Simatic IPC BX-21 to Simatic IPC
 
  - Fix-ups
    - Some dependency / Kconfig tweaking
    - Move final probe() functions back over from .probe_new()
    - Simplify obtaining resources (memory, device data) using unified API helpers
    - Bunch of Device Tree additions, conversions and adaptions
    - Fix trivial styling issues; comments
    - Ensure correct includes are present and remove some that are not required
    - Omit the use of redundant casts and if relevant replace with better ones
    - Use purpose-built APIs for various actions; sysfs_emit(), module_led_trigger()
    - Remove a bunch of superfluous locking
 
  - Bug Fixes
    - Ensure error codes are correctly propagated back up the call chain
    - Fix incorrect error values from being returned (missing '-')
    - Ensure get'ed resources are put'ed to prevent leaks
    - Use correct class when exporting module resources
    - Fixing rounding (or lack there of) issues
    - Fix 'always false' LED_COLOR_ID_MULTI BUG() check
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Merge tag 'leds-next-6.6' of git://git.kernel.org/pub/scm/linux/kernel/git/lee/leds

Pull LED updates from Lee Jones:
 "Core Frameworks:
   - Add new framework to support Group Multi-Color (GMC) LEDs
   - Offer an 'optional' API for non-essential LEDs
   - Support obtaining 'max brightness' values from Device Tree
   - Provide new led_classdev member 'color' (settable via DT and SYFS)
   - Stop TTY Trigger from using the old LED_ON constraints
   - Statically allocate leds_class

  New Drivers:
   - Add support for NXP PCA995x I2C Constant Current LED Driver

  New Device Support:
   - Add support for Siemens Simatic IPC BX-21 to Simatic IPC

  Fix-ups:
   - Some dependency / Kconfig tweaking
   - Move final probe() functions back over from .probe_new()
   - Simplify obtaining resources (memory, device data) using unified
     API helpers
   - Bunch of Device Tree additions, conversions and adaptions
   - Fix trivial styling issues; comments
   - Ensure correct includes are present and remove some that are not
     required
   - Omit the use of redundant casts and if relevant replace with better
     ones
   - Use purpose-built APIs for various actions; sysfs_emit(),
     module_led_trigger()
   - Remove a bunch of superfluous locking

  Bug Fixes:
   - Ensure error codes are correctly propagated back up the call chain
   - Fix incorrect error values from being returned (missing '-')
   - Ensure get'ed resources are put'ed to prevent leaks
   - Use correct class when exporting module resources
   - Fixing rounding (or lack there of) issues
   - Fix 'always false' LED_COLOR_ID_MULTI BUG() check"

* tag 'leds-next-6.6' of git://git.kernel.org/pub/scm/linux/kernel/git/lee/leds: (40 commits)
  leds: aw2013: Enable pull-up supply for interrupt and I2C
  dt-bindings: leds: Document pull-up supply for interrupt and I2C
  dt-bindings: leds: aw2013: Document interrupt
  leds: uleds: Use module_misc_device macro to simplify the code
  leds: trigger: netdev: Use module_led_trigger macro to simplify the code
  dt-bindings: leds: Fix reference to definition of default-state
  leds: turris-omnia: Drop unnecessary mutex locking
  leds: turris-omnia: Use sysfs_emit() instead of sprintf()
  leds: Make leds_class a static const structure
  leds: Remove redundant of_match_ptr()
  dt-bindings: leds: Add gpio-line-names to PCA9532 GPIO
  leds: trigger: tty: Do not use LED_ON/OFF constants, use led_blink_set_oneshot instead
  dt-bindings: leds: rohm,bd71828: Drop select:false
  leds: Fix BUG_ON check for LED_COLOR_ID_MULTI that is always false
  leds: multicolor: Use rounded division when calculating color components
  leds: rgb: Add a multicolor LED driver to group monochromatic LEDs
  dt-bindings: leds: Add binding for a multicolor group of LEDs
  leds: class: Store the color index in struct led_classdev
  leds: Provide devm_of_led_get_optional()
  leds: pca995x: Fix MODULE_DEVICE_TABLE for OF
  ...
2023-09-04 13:52:58 -07:00
..
obsolete docs: update ocfs2-devel mailing list address 2023-07-08 09:29:29 -07:00
removed docs: update ocfs2-devel mailing list address 2023-07-08 09:29:29 -07:00
stable dmaengine updates for v6.6 2023-09-03 10:49:42 -07:00
testing - Core Frameworks 2023-09-04 13:52:58 -07:00
README docs: ABI: README: specify that files should be ReST compatible 2020-10-30 13:07:01 +01:00

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.


Note:
   The fields should be use a simple notation, compatible with ReST markup.
   Also, the file **should not** have a top-level index, like::

	===
	foo
	===

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.