WSL2-Linux-Kernel/Documentation/ABI
Linus Torvalds f187e9fd68 Merge branch 'perf-urgent-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip
Pull perf updates and fixes from Ingo Molnar:
 "It's mostly fixes, but there's also two late items:

   - preliminary GTK GUI support for perf report
   - PMU raw event format descriptors in sysfs, to be parsed by tooling

  The raw event format in sysfs is a new ABI.  For example for the 'CPU'
  PMU we have:

    aldebaran:~> ll /sys/bus/event_source/devices/cpu/format/*
    -r--r--r--. 1 root root 4096 Mar 31 10:29 /sys/bus/event_source/devices/cpu/format/any
    -r--r--r--. 1 root root 4096 Mar 31 10:29 /sys/bus/event_source/devices/cpu/format/cmask
    -r--r--r--. 1 root root 4096 Mar 31 10:29 /sys/bus/event_source/devices/cpu/format/edge
    -r--r--r--. 1 root root 4096 Mar 31 10:29 /sys/bus/event_source/devices/cpu/format/event
    -r--r--r--. 1 root root 4096 Mar 31 10:29 /sys/bus/event_source/devices/cpu/format/inv
    -r--r--r--. 1 root root 4096 Mar 31 10:29 /sys/bus/event_source/devices/cpu/format/offcore_rsp
    -r--r--r--. 1 root root 4096 Mar 31 10:29 /sys/bus/event_source/devices/cpu/format/pc
    -r--r--r--. 1 root root 4096 Mar 31 10:29 /sys/bus/event_source/devices/cpu/format/umask

  those lists of fields contain a specific format:

    aldebaran:~> cat /sys/bus/event_source/devices/cpu/format/offcore_rsp
    config1:0-63

  So, those who wish to specify raw events can now use the following
  event format:

    -e cpu/cmask=1,event=2,umask=3

  Most people will not want to specify any events (let alone raw
  events), they'll just use whatever default event the tools use.

  But for more obscure PMU events that have no cross-architecture
  generic events the above syntax is more usable and a bit more
  structured than specifying hex numbers."

* 'perf-urgent-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip: (41 commits)
  perf tools: Remove auto-generated bison/flex files
  perf annotate: Fix off by one symbol hist size allocation and hit accounting
  perf tools: Add missing ref-cycles event back to event parser
  perf annotate: addr2line wants addresses in same format as objdump
  perf probe: Finder fails to resolve function name to address
  tracing: Fix ent_size in trace output
  perf symbols: Handle NULL dso in dso__name_len
  perf symbols: Do not include libgen.h
  perf tools: Fix bug in raw sample parsing
  perf tools: Fix display of first level of callchains
  perf tools: Switch module.h into export.h
  perf: Move mmap page data_head offset assertion out of header
  perf: Fix mmap_page capabilities and docs
  perf diff: Fix to work with new hists design
  perf tools: Fix modifier to be applied on correct events
  perf tools: Fix various casting issues for 32 bits
  perf tools: Simplify event_read_id exit path
  tracing: Fix ftrace stack trace entries
  tracing: Move the tracing_on/off() declarations into CONFIG_TRACING
  perf report: Add a simple GTK2-based 'perf report' browser
  ...
2012-03-31 13:34:04 -07:00
..
obsolete Documentation: Fix multiple typo in Documentation 2012-03-07 16:08:24 +01:00
removed driver-core: documentation: fix up Greg's email address 2012-02-15 14:48:01 -08:00
stable Documentation: fix typo in ABI/stable/sysfs-driver-usb-usbtmc 2012-03-30 16:03:15 -07:00
testing Merge branch 'perf-urgent-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip 2012-03-31 13:34:04 -07:00
README [PATCH] Add kernel<->userspace ABI stability documentation 2006-06-21 12:40:47 -07:00

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.
	The file Documentation/feature-removal-schedule.txt may describe
	some of these interfaces, giving a schedule for when they will
	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.