Subversion Repositories or1k_soc_on_altera_embedded_dev_kit

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        why it is obsolete and when it can be expected to be removed.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.