linux/Documentation/ABI
Linus Torvalds 63de37476e chrome platform changes for v5.5
* CrOS EC / MFD / IIO
  - Contains tag-ib-chrome-mfd-iio-input-5.5, which is the first part of a
    series from Gwendal to refactor sensor code between MFD, CrOS EC, iio
    and input in order to add a new sensorhub driver and FIFO processing
 
 * Wilco EC:
  - Add support for Dell's USB PowerShare policy control, keyboard
    backlight LED driver, and a new test_event file.
  - Fixes use after free in wilco_ec's telemetry driver.
 
 * Misc:
  - bugfix in cros_usbpd_logger (missing destroy workqueue).
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Merge tag 'tag-chrome-platform-for-v5.5' of git://git.kernel.org/pub/scm/linux/kernel/git/chrome-platform/linux

Pull chrome platform changes from Benson Leung:
 "CrOS EC / MFD / IIO:

   - Contains tag-ib-chrome-mfd-iio-input-5.5, which is the first part
     of a series from Gwendal to refactor sensor code between MFD, CrOS
     EC, iio and input in order to add a new sensorhub driver and FIFO
     processing

  Wilco EC:

   - Add support for Dell's USB PowerShare policy control, keyboard
     backlight LED driver, and a new test_event file.

   - Fixes use after free in wilco_ec's telemetry driver.

  Misc:

   - bugfix in cros_usbpd_logger (missing destroy workqueue)"

* tag 'tag-chrome-platform-for-v5.5' of git://git.kernel.org/pub/scm/linux/kernel/git/chrome-platform/linux:
  platform/chrome: wilco_ec: fix use after free issue
  platform/chrome: cros_ec: Add Kconfig default for cros-ec-sensorhub
  Revert "Input: cros_ec_keyb: mask out extra flags in event_type"
  Revert "Input: cros_ec_keyb - add back missing mask for event_type"
  platform/chrome: cros_ec: handle MKBP more events flag
  platform/chrome: cros_ec: Do not attempt to register a non-positive IRQ number
  platform/chrome: cros-ec: Record event timestamp in the hard irq
  mfd / platform / iio: cros_ec: Register sensor through sensorhub
  iio / platform: cros_ec: Add cros-ec-sensorhub driver
  mfd / platform: cros_ec: Add sensor_count and make check_features public
  platform/chrome: cros_ec: Put docs with the code
  platform/chrome: cros_usbpd_logger: add missed destroy_workqueue in remove
  platform/chrome: cros_ec: Fix Kconfig indentation
  platform/chrome: wilco_ec: Add keyboard backlight LED support
  platform/chrome: wilco_ec: Add charging config driver
  platform/chrome: wilco_ec: Add Dell's USB PowerShare Policy control
  platform/chrome: wilco_ec: Add debugfs test_event file
2019-12-03 14:37:12 -08:00
..
obsolete docs: gpio: add sysfs interface to the admin-guide 2019-07-15 11:03:03 -03:00
removed docs: driver-api: add a series of orphaned documents 2019-07-15 11:03:02 -03:00
stable TTY/Serial patches for 5.5-rc1 2019-12-03 14:09:14 -08:00
testing chrome platform changes for v5.5 2019-12-03 14:37:12 -08:00
README

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.