linux/Documentation/ABI
Linus Torvalds 385336e321 platform-drivers-x86 for 3.19
thinkpad-acpi: Switch to software mute, cleanups
 acerhdf: Bang-bang thermal governor, new models, cleanups
 dell-laptop: New keyboard backlight support and documentation
 toshiba_acpi: Keyboard backlight updates, hotkey handling
 dell-wmi: Keypress filtering, WMI event processing
 eeepc-laptop: Multiple cleanups, improved error handling, documentation
 hp_wireless: Inform the user if hp_wireless_input_setup()/add() fails
 misc: Code cleanups, quirks, various new IDs
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Merge tag 'platform-drivers-x86-v3.19-1' of git://git.infradead.org/users/dvhart/linux-platform-drivers-x86

Pull x86 platform driver update from Darren Hart:
 - thinkpad-acpi: Switch to software mute, cleanups
 - acerhdf: Bang-bang thermal governor, new models, cleanups
 - dell-laptop: New keyboard backlight support and documentation
 - toshiba_acpi: Keyboard backlight updates, hotkey handling
 - dell-wmi: Keypress filtering, WMI event processing
 - eeepc-laptop: Multiple cleanups, improved error handling, documentation
 - hp_wireless: Inform the user if hp_wireless_input_setup()/add() fails
 - misc: Code cleanups, quirks, various new IDs

* tag 'platform-drivers-x86-v3.19-1' of git://git.infradead.org/users/dvhart/linux-platform-drivers-x86: (33 commits)
  platform/x86/acerhdf: Still depends on THERMAL
  Documentation: Add entry for dell-laptop sysfs interface
  acpi: Remove _OSI(Linux) for ThinkPads
  thinkpad-acpi: Try to use full software mute control
  acerhdf: minor clean up
  acerhdf: added critical trip point
  acerhdf: Use bang-bang thermal governor
  acerhdf: Adding support for new models
  acerhdf: Adding support for "manual mode"
  dell-smo8800: Add more ACPI ids and change description of driver
  platform: x86: dell-laptop: Add support for keyboard backlight
  toshiba_acpi: Add keyboard backlight mode change event
  toshiba_acpi: Change notify funtion to handle more events
  toshiba_acpi: Move hotkey enabling code to its own function
  dell-wmi: Don't report keypresses on keybord illumination change
  dell-wmi: Don't report keypresses for radio state changes
  hp_wireless: Inform the user if hp_wireless_input_setup()/add() fails
  toshiba-acpi: Add missing ID (TOS6207)
  Sony-laptop: Deletion of an unnecessary check before the function call "pci_dev_put"
  platform: x86: Deletion of checks before backlight_device_unregister()
  ...
2014-12-18 20:24:55 -08:00
..
obsolete
removed net_dma: simple removal 2014-09-28 07:05:16 -07:00
stable USB patches for 3.19-rc1 2014-12-14 14:57:16 -08:00
testing platform-drivers-x86 for 3.19 2014-12-18 20:24:55 -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/stable_api_nonsense.txt.