[PATCH] Add kernel<->userspace ABI stability documentation
Signed-off-by: Kay Sievers <kay.sievers@suse.de>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>
diff --git a/Documentation/ABI/README b/Documentation/ABI/README
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+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+ why it is obsolete and when it can be expected to be removed.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.
diff --git a/Documentation/ABI/obsolete/devfs b/Documentation/ABI/obsolete/devfs
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+What: devfs
+Date: July 2005
+Contact: Greg Kroah-Hartman <gregkh@suse.de>
+Description:
+ devfs has been unmaintained for a number of years, has unfixable
+ races, contains a naming policy within the kernel that is
+ against the LSB, and can be replaced by using udev.
+ The files fs/devfs/*, include/linux/devfs_fs*.h will be removed,
+ along with the the assorted devfs function calls throughout the
+ kernel tree.
+
+Users:
+
diff --git a/Documentation/ABI/stable/syscalls b/Documentation/ABI/stable/syscalls
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+What: The kernel syscall interface
+Description:
+ This interface matches much of the POSIX interface and is based
+ on it and other Unix based interfaces. It will only be added to
+ over time, and not have things removed from it.
+
+ Note that this interface is different for every architecture
+ that Linux supports. Please see the architecture-specific
+ documentation for details on the syscall numbers that are to be
+ mapped to each syscall.
diff --git a/Documentation/ABI/stable/sysfs-module b/Documentation/ABI/stable/sysfs-module
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+What: /sys/module
+Description:
+ The /sys/module tree consists of the following structure:
+
+ /sys/module/MODULENAME
+ The name of the module that is in the kernel. This
+ module name will show up either if the module is built
+ directly into the kernel, or if it is loaded as a
+ dyanmic module.
+
+ /sys/module/MODULENAME/parameters
+ This directory contains individual files that are each
+ individual parameters of the module that are able to be
+ changed at runtime. See the individual module
+ documentation as to the contents of these parameters and
+ what they accomplish.
+
+ Note: The individual parameter names and values are not
+ considered stable, only the fact that they will be
+ placed in this location within sysfs. See the
+ individual driver documentation for details as to the
+ stability of the different parameters.
+
+ /sys/module/MODULENAME/refcnt
+ If the module is able to be unloaded from the kernel, this file
+ will contain the current reference count of the module.
+
+ Note: If the module is built into the kernel, or if the
+ CONFIG_MODULE_UNLOAD kernel configuration value is not enabled,
+ this file will not be present.
diff --git a/Documentation/ABI/testing/sysfs-class b/Documentation/ABI/testing/sysfs-class
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+What: /sys/class/
+Date: Febuary 2006
+Contact: Greg Kroah-Hartman <gregkh@suse.de>
+Description:
+ The /sys/class directory will consist of a group of
+ subdirectories describing individual classes of devices
+ in the kernel. The individual directories will consist
+ of either subdirectories, or symlinks to other
+ directories.
+
+ All programs that use this directory tree must be able
+ to handle both subdirectories or symlinks in order to
+ work properly.
+
+Users:
+ udev <linux-hotplug-devel@lists.sourceforge.net>
diff --git a/Documentation/ABI/testing/sysfs-devices b/Documentation/ABI/testing/sysfs-devices
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+What: /sys/devices
+Date: February 2006
+Contact: Greg Kroah-Hartman <gregkh@suse.de>
+Description:
+ The /sys/devices tree contains a snapshot of the
+ internal state of the kernel device tree. Devices will
+ be added and removed dynamically as the machine runs,
+ and between different kernel versions, the layout of the
+ devices within this tree will change.
+
+ Please do not rely on the format of this tree because of
+ this. If a program wishes to find different things in
+ the tree, please use the /sys/class structure and rely
+ on the symlinks there to point to the proper location
+ within the /sys/devices tree of the individual devices.
+ Or rely on the uevent messages to notify programs of
+ devices being added and removed from this tree to find
+ the location of those devices.
+
+ Note that sometimes not all devices along the directory
+ chain will have emitted uevent messages, so userspace
+ programs must be able to handle such occurrences.
+
+Users:
+ udev <linux-hotplug-devel@lists.sourceforge.net>
