linux/Documentation/ABI
Linus Torvalds da01e61428 Merge tag 'f2fs-for-3.18' of git://git.kernel.org/pub/scm/linux/kernel/git/jaegeuk/f2fs
Pull f2fs updates from Jaegeuk Kim:
 "This patch-set introduces a couple of new features such as large
  sector size, FITRIM, and atomic/volatile writes.

  Several patches enhance power-off recovery and checkpoint routines.

  The fsck.f2fs starts to support fixing corrupted partitions with
  recovery hints provided by this patch-set.

  Summary:
   - retain some recovery information for fsck.f2fs
   - enhance checkpoint speed
   - enhance flush command management
   - bug fix for lseek
   - tune in-place-update policies
   - enhance roll-forward speed
   - revisit all the roll-forward and fsync rules
   - support larget sector size
   - support FITRIM
   - support atomic and volatile writes

  And several clean-ups and bug fixes are included"

* tag 'f2fs-for-3.18' of git://git.kernel.org/pub/scm/linux/kernel/git/jaegeuk/f2fs: (42 commits)
  f2fs: support volatile operations for transient data
  f2fs: support atomic writes
  f2fs: remove unused return value
  f2fs: clean up f2fs_ioctl functions
  f2fs: potential shift wrapping buf in f2fs_trim_fs()
  f2fs: call f2fs_unlock_op after error was handled
  f2fs: check the use of macros on block counts and addresses
  f2fs: refactor flush_nat_entries to remove costly reorganizing ops
  f2fs: introduce FITRIM in f2fs_ioctl
  f2fs: introduce cp_control structure
  f2fs: use more free segments until SSR is activated
  f2fs: change the ipu_policy option to enable combinations
  f2fs: fix to search whole dirty segmap when get_victim
  f2fs: fix to clean previous mount option when remount_fs
  f2fs: skip punching hole in special condition
  f2fs: support large sector size
  f2fs: fix to truncate blocks past EOF in ->setattr
  f2fs: update i_size when __allocate_data_block
  f2fs: use MAX_BIO_BLOCKS(sbi)
  f2fs: remove redundant operation during roll-forward recovery
  ...
2014-10-08 12:53:15 -04:00
..
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 net_dma: simple removal 2014-09-28 07:05:16 -07:00
stable Documentation: sysfs-bus-usb: update power/persist description 2014-07-09 16:11:11 -07:00
testing Merge tag 'f2fs-for-3.18' of git://git.kernel.org/pub/scm/linux/kernel/git/jaegeuk/f2fs 2014-10-08 12:53:15 -04:00
README Documentation/ABI: document the non-ABI status of Kconfig and symbols 2013-11-13 12:09:32 +09:00

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/stable_api_nonsense.txt.