linux/Documentation/ABI
Linus Torvalds d891ea23d5 Merge branch 'for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/sage/ceph-client
Pull ceph updates from Sage Weil:
 "This is a big batch.  From Ilya we have:

   - rbd support for more than ~250 mapped devices (now uses same scheme
     that SCSI does for device major/minor numbering)
   - crush updates for new mapping behaviors (will be needed for coming
     erasure coding support, among other things)
   - preliminary support for tiered storage pools

  There is also a big series fixing a pile cephfs bugs with clustered
  MDSs from Yan Zheng, ACL support for cephfs from Guangliang Zhao, ceph
  fscache improvements from Li Wang, improved behavior when we get
  ENOSPC from Josh Durgin, some readv/writev improvements from
  Majianpeng, and the usual mix of small cleanups"

* 'for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/sage/ceph-client: (76 commits)
  ceph: cast PAGE_SIZE to size_t in ceph_sync_write()
  ceph: fix dout() compile warnings in ceph_filemap_fault()
  libceph: support CEPH_FEATURE_OSD_CACHEPOOL feature
  libceph: follow redirect replies from osds
  libceph: rename ceph_osd_request::r_{oloc,oid} to r_base_{oloc,oid}
  libceph: follow {read,write}_tier fields on osd request submission
  libceph: add ceph_pg_pool_by_id()
  libceph: CEPH_OSD_FLAG_* enum update
  libceph: replace ceph_calc_ceph_pg() with ceph_oloc_oid_to_pg()
  libceph: introduce and start using oid abstraction
  libceph: rename MAX_OBJ_NAME_SIZE to CEPH_MAX_OID_NAME_LEN
  libceph: move ceph_file_layout helpers to ceph_fs.h
  libceph: start using oloc abstraction
  libceph: dout() is missing a newline
  libceph: add ceph_kv{malloc,free}() and switch to them
  libceph: support CEPH_FEATURE_EXPORT_PEER
  ceph: add imported caps when handling cap export message
  ceph: add open export target session helper
  ceph: remove exported caps when handling cap import message
  ceph: handle session flush message
  ...
2014-01-28 11:02:23 -08:00
..
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 IB/srp: Make queue size configurable 2013-11-08 14:43:17 -08:00
testing Merge branch 'for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/sage/ceph-client 2014-01-28 11:02:23 -08:00
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.