On Thu, 27 Apr 2006 14:10:12 -0700 Greg KH wrote:
> In short, we really need a way to document the different interfaces that
> the kernel has between userspace and kernelspace. Traditionally this
> has only been with the syscall interface, and a few odd proc files and
> sysctls. In recent years that interface has grown to accommodate a
> variety of ram-based filesystems, and other fun ways to get data in and
> out of the kernel (netlink, connector, etc.)
>
> This patch proposes that _all_ kernel interfaces between userspace and
> the kernel be documented in some manner. Now this doesn't mean that the
> man-pages for the different syscalls need to be included here, but we
> really need to try to get a handle of what is changing and what will be
> affected if we do change things.
Yes. Thank you.
> --------------
>
> --- /dev/null
> +++ gregkh-2.6/Documentation/ABI/README
> @@ -0,0 +1,77 @@
> +This directory attempts to document the ABI between the Linux kernel and
> +userspace, and the relative stability of these interfaces. Due to the
> +ever changing nature of Linux, and the differing maturity levels, these
everchanging
> +interfaces should be used by userspace programs in different ways.
> +
> +We have four different levels of ABI stability, as shown by the four
> +different subdirectorys in this location. Interfaces may change levels
subdirectories
> +of stability according to the rules described below.
> +
> +The different levels of stability are:
> +
> + stable/
> + This directory documents the interfaces that have the developer
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 simple interfaces (like syscalls) are expected to never
> + change and always be available.
IMO "Most simple interfaces" isn't explicit enough. We could argue
all day on which interfaces are simple and which are not.
> +
> + 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 for
drop ending "for"
> + 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 states:
s/states/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 can not be removed from the
"cannot"
> +kernel tree without going through the obsolete state first.
> +
> +It's up to the developer to place their interface in the category they
s/their/an/
better: s/their interface/interfaces/
> +wish for it to start out in.
> --- /dev/null
> +++ gregkh-2.6/Documentation/ABI/obsolete/devfs
> @@ -0,0 +1,13 @@
> +What: devfs
> +Date: July 2005
> +Contact: Greg Kroah-Hartman <[email protected]>
> +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:
> +
> --- /dev/null
> +++ gregkh-2.6/Documentation/ABI/stable/syscalls
> @@ -0,0 +1,10 @@
> +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 arch specific documentation
"arch-specific" or "architecture-specific"
> + for details on the syscall numbers that are to be mapped to each
> + syscall.
> --- /dev/null
> +++ gregkh-2.6/Documentation/ABI/stable/sysfs-module
> @@ -0,0 +1,29 @@
> +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 both if the module is built
s/both/either/
> + 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 into the module that are are able to be
drop one "are"
s/into/of/
> + 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 into
s/into/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.
> --- /dev/null
> +++ gregkh-2.6/Documentation/ABI/testing/sysfs-class
> @@ -0,0 +1,16 @@
> +What: /sys/class/
> +Date: Febuary 2006
> +Contact: Greg Kroah-Hartman <[email protected]>
> +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 <[email protected]>
> --- /dev/null
> +++ gregkh-2.6/Documentation/ABI/testing/sysfs-devices
> @@ -0,0 +1,25 @@
> +What: /sys/devices
> +Date: February 2006
> +Contact: Greg Kroah-Hartman <[email protected]>
> +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 occurances.
"occurrences"
So where is the uevent message interface documented?
> +
> +Users:
> + udev <[email protected]>
> -
---
~Randy
-
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