1.. SPDX-License-Identifier: BSD-3-Clause 2 3============================== 4Netlink spec C code generation 5============================== 6 7This document describes how Netlink specifications are used to render 8C code (uAPI, policies etc.). It also defines the additional properties 9allowed in older families by the ``genetlink-c`` protocol level, 10to control the naming. 11 12For brevity this document refers to ``name`` properties of various 13objects by the object type. For example ``$attr`` is the value 14of ``name`` in an attribute, and ``$family`` is the name of the 15family (the global ``name`` property). 16 17The upper case is used to denote literal values, e.g. ``$family-CMD`` 18means the concatenation of ``$family``, a dash character, and the literal 19``CMD``. 20 21The names of ``#defines`` and enum values are always converted to upper case, 22and with dashes (``-``) replaced by underscores (``_``). 23 24If the constructed name is a C keyword, an extra underscore is 25appended (``do`` -> ``do_``). 26 27Globals 28======= 29 30``c-family-name`` controls the name of the ``#define`` for the family 31name, default is ``$family-FAMILY-NAME``. 32 33``c-version-name`` controls the name of the ``#define`` for the version 34of the family, default is ``$family-FAMILY-VERSION``. 35 36``max-by-define`` selects if max values for enums are defined as a 37``#define`` rather than inside the enum. 38 39Definitions 40=========== 41 42Constants 43--------- 44 45Every constant is rendered as a ``#define``. 46The name of the constant is ``$family-$constant`` and the value 47is rendered as a string or integer according to its type in the spec. 48 49Enums and flags 50--------------- 51 52Enums are named ``$family-$enum``. The full name can be set directly 53or suppressed by specifying the ``enum-name`` property. 54Default entry name is ``$family-$enum-$entry``. 55If ``name-prefix`` is specified it replaces the ``$family-$enum`` 56portion of the entry name. 57 58Boolean ``render-max`` controls creation of the max values 59(which are enabled by default for attribute enums). 60 61Attributes 62========== 63 64Each attribute set (excluding fractional sets) is rendered as an enum. 65 66Attribute enums are traditionally unnamed in netlink headers. 67If naming is desired ``enum-name`` can be used to specify the name. 68 69The default attribute name prefix is ``$family-A`` if the name of the set 70is the same as the name of the family and ``$family-A-$set`` if the names 71differ. The prefix can be overridden by the ``name-prefix`` property of a set. 72The rest of the section will refer to the prefix as ``$pfx``. 73 74Attributes are named ``$pfx-$attribute``. 75 76Attribute enums end with two special values ``__$pfx-MAX`` and ``$pfx-MAX`` 77which are used for sizing attribute tables. 78These two names can be specified directly with the ``attr-cnt-name`` 79and ``attr-max-name`` properties respectively. 80 81If ``max-by-define`` is set to ``true`` at the global level ``attr-max-name`` 82will be specified as a ``#define`` rather than an enum value. 83 84Operations 85========== 86 87Operations are named ``$family-CMD-$operation``. 88If ``name-prefix`` is specified it replaces the ``$family-CMD`` 89portion of the name. 90 91Similarly to attribute enums operation enums end with special count and max 92attributes. 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`` 94is ``true``. 95 96Multicast groups 97================ 98 99Each multicast group gets a define rendered into the kernel uAPI header. 100The name of the define is ``$family-MCGRP-$group``, and can be overwritten 101with the ``c-define-name`` property. 102 103Code generation 104=============== 105 106uAPI header is assumed to come from ``<linux/$family.h>`` in the default header 107search path. It can be changed using the ``uapi-header`` global property. 108