1 .. SPDX-License-Identifier: BSD-3-Clause
3 ==============================
4 Netlink spec C code generation
5 ==============================
7 This document describes how Netlink specifications are used to render
8 C code (uAPI, policies etc.). It also defines the additional properties
9 allowed in older families by the ``genetlink-c`` protocol level,
10 to control the naming.
12 For brevity this document refers to ``name`` properties of various
13 objects by the object type. For example ``$attr`` is the value
14 of ``name`` in an attribute, and ``$family`` is the name of the
15 family (the global ``name`` property).
17 The upper case is used to denote literal values, e.g. ``$family-CMD``
18 means the concatenation of ``$family``, a dash character, and the literal
21 The names of ``#defines`` and enum values are always converted to upper case,
22 and with dashes (``-``) replaced by underscores (``_``).
24 If the constructed name is a C keyword, an extra underscore is
25 appended (``do`` -> ``do_``).
30 ``c-family-name`` controls the name of the ``#define`` for the family
31 name, default is ``$family-FAMILY-NAME``.
33 ``c-version-name`` controls the name of the ``#define`` for the version
34 of the family, default is ``$family-FAMILY-VERSION``.
36 ``max-by-define`` selects if max values for enums are defined as a
37 ``#define`` rather than inside the enum.
45 Every constant is rendered as a ``#define``.
46 The name of the constant is ``$family-$constant`` and the value
47 is rendered as a string or integer according to its type in the spec.
52 Enums are named ``$family-$enum``. The full name can be set directly
53 or suppressed by specifying the ``enum-name`` property.
54 Default entry name is ``$family-$enum-$entry``.
55 If ``name-prefix`` is specified it replaces the ``$family-$enum``
56 portion of the entry name.
58 Boolean ``render-max`` controls creation of the max values
59 (which are enabled by default for attribute enums).
64 Each attribute set (excluding fractional sets) is rendered as an enum.
66 Attribute enums are traditionally unnamed in netlink headers.
67 If naming is desired ``enum-name`` can be used to specify the name.
69 The default attribute name prefix is ``$family-A`` if the name of the set
70 is the same as the name of the family and ``$family-A-$set`` if the names
71 differ. The prefix can be overridden by the ``name-prefix`` property of a set.
72 The rest of the section will refer to the prefix as ``$pfx``.
74 Attributes are named ``$pfx-$attribute``.
76 Attribute enums end with two special values ``__$pfx-MAX`` and ``$pfx-MAX``
77 which are used for sizing attribute tables.
78 These two names can be specified directly with the ``attr-cnt-name``
79 and ``attr-max-name`` properties respectively.
81 If ``max-by-define`` is set to ``true`` at the global level ``attr-max-name``
82 will be specified as a ``#define`` rather than an enum value.
87 Operations are named ``$family-CMD-$operation``.
88 If ``name-prefix`` is specified it replaces the ``$family-CMD``
91 Similarly to attribute enums operation enums end with special count and max
92 attributes. For operations those attributes can be renamed with
93 ``cmd-cnt-name`` and ``cmd-max-name``. Max will be a define if ``max-by-define``
99 Each multicast group gets a define rendered into the kernel uAPI header.
100 The name of the define is ``$family-MCGRP-$group``, and can be overwritten
101 with the ``c-define-name`` property.
106 uAPI header is assumed to come from ``<linux/$family.h>`` in the default header
107 search path. It can be changed using the ``uapi-header`` global property.