linux/Documentation/ABI
Greg Kroah-Hartman f641f66784 First round of new drivers, cleanups and functionality for the 3.17 cycle.
New drivers
 * t5403 barometric pressure sensor
 * kxcjk1013 accelerometer (with a locking followup fix).
 * ak09911 digital compass
 
 Documentation
 * ABI docs for proximity added (interface has been there a long time but
   somehow snuck through without being documented)
 * Move iio-trig-sysfs documentation out of staging (got left behind when
   the driver moved some time ago).
 
 Cleanups
  * drop the timestamp argument from iio_trigger_poll(_chained) as
    nothing has been done with it for some time.
  * ad799x kerneldoc for ad799x_chip brought up to date.
  * replace a number of reimplementations of the GENMASK macro and
    use the BIT macro to cleanup a few locations.
  * bring the iio_event_monitor example program up to date with new
    device types.
  * fix some incorrect function prototypes in iio_utils.h example code.
  * INDIO_RING_TRIGGERED to INDIO_BUFFER_TRIGGERED fix in docs. This
    got left behind after we renamed it a long time back.
  * fix error handling in the generic_buffer example program.
  * small tidy ups in the iio-trig-periodic-rtc driver.
  * Allow reseting iio-trig-periodic-rtc frequency to 0 (default) after
    it has changed.
  * Trivial tidy ups in coding style in iio_simply_dummy
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Merge tag 'iio-for-3.17a' of git://git.kernel.org/pub/scm/linux/kernel/git/jic23/iio into staging-next

Jonathan writes:

First round of new drivers, cleanups and functionality for the 3.17 cycle.

New drivers
* t5403 barometric pressure sensor
* kxcjk1013 accelerometer (with a locking followup fix).
* ak09911 digital compass

Documentation
* ABI docs for proximity added (interface has been there a long time but
  somehow snuck through without being documented)
* Move iio-trig-sysfs documentation out of staging (got left behind when
  the driver moved some time ago).

Cleanups
 * drop the timestamp argument from iio_trigger_poll(_chained) as
   nothing has been done with it for some time.
 * ad799x kerneldoc for ad799x_chip brought up to date.
 * replace a number of reimplementations of the GENMASK macro and
   use the BIT macro to cleanup a few locations.
 * bring the iio_event_monitor example program up to date with new
   device types.
 * fix some incorrect function prototypes in iio_utils.h example code.
 * INDIO_RING_TRIGGERED to INDIO_BUFFER_TRIGGERED fix in docs. This
   got left behind after we renamed it a long time back.
 * fix error handling in the generic_buffer example program.
 * small tidy ups in the iio-trig-periodic-rtc driver.
 * Allow reseting iio-trig-periodic-rtc frequency to 0 (default) after
   it has changed.
 * Trivial tidy ups in coding style in iio_simply_dummy
2014-06-18 20:02:33 -07:00
..
obsolete Merge branches 'for-3.7/upstream-fixes', 'for-3.8/hidraw', 'for-3.8/i2c-hid', 'for-3.8/multitouch', 'for-3.8/roccat', 'for-3.8/sensors' and 'for-3.8/upstream' into for-linus 2012-12-12 21:41:55 +01:00
removed netfilter: remove ip_queue support 2012-05-08 20:25:42 +02:00
stable powerpc: Document sysfs DSCR interface 2014-05-28 13:35:40 +10:00
testing First round of new drivers, cleanups and functionality for the 3.17 cycle. 2014-06-18 20:02:33 -07:00
README Documentation/ABI: document the non-ABI status of Kconfig and symbols 2013-11-13 12:09:32 +09:00

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.