1 This directory attempts to document the ABI be
2 userspace, and the relative stability of these
3 everchanging nature of Linux, and the differin
4 interfaces should be used by userspace program
5
6 We have four different levels of ABI stability
7 different subdirectories in this location. In
8 of stability according to the rules described
9
10 The different levels of stability are:
11
12 stable/
13 This directory documents the interface
14 defined to be stable. Userspace progr
15 interfaces with no restrictions, and b
16 them will be guaranteed for at least 2
17 (like syscalls) are expected to never
18 available.
19
20 testing/
21 This directory documents interfaces th
22 as the main development of this interf
23 The interface can be changed to add ne
24 current interface will not break by do
25 errors or security problems are found
26 programs can start to rely on these in
27 aware of changes that can occur before
28 be marked stable. Programs that use t
29 strongly encouraged to add their name
30 these interfaces, so that the kernel d
31 notify them if any changes occur (see
32 layout of the files below for details
33
34 obsolete/
35 This directory documents interfaces th
36 the kernel, but are marked to be remov
37 time. The description of the interfac
38 why it is obsolete and when it can be
39
40 removed/
41 This directory contains a list of the
42 been removed from the kernel.
43
44 Every file in these directories will contain t
45
46 What: Short description of the inter
47 Date: Date created
48 KernelVersion: Kernel version this feature fi
49 Contact: Primary contact for this inter
50 Description: Long description of the interf
51 Users: All users of this interface wh
52 it changes. This is very impo
53 the "testing" stage, so that k
54 with userspace developers to e
55 break in ways that are unaccep
56 important to get feedback for
57 sure they are working in a pro
58 be changed further.
59
60
61 Note:
62 The fields should be use a simple notation,
63 Also, the file **should not** have a top-le
64
65 ===
66 foo
67 ===
68
69 How things move between levels:
70
71 Interfaces in stable may move to obsolete, as
72 notification is given.
73
74 Interfaces may be removed from obsolete and th
75 documented amount of time has gone by.
76
77 Interfaces in the testing state can move to th
78 developers feel they are finished. They canno
79 kernel tree without going through the obsolete
80
81 It's up to the developer to place their interf
82 wish for it to start out in.
83
84
85 Notable bits of non-ABI, which should not unde
86 stable:
87
88 - Kconfig. Userspace should not rely on the p
89 particular Kconfig symbol, in /proc/config.g
90 commonly installed to /boot, or in any invoc
91 process.
92
93 - Kernel-internal symbols. Do not rely on the
94 type of any kernel symbol, either in System.
95 itself. See Documentation/process/stable-ap
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