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1.. SPDX-License-Identifier: BSD-3-Clause2 3==============================4Netlink spec C code generation5==============================6 7This document describes how Netlink specifications are used to render8C code (uAPI, policies etc.). It also defines the additional properties9allowed in older families by the ``genetlink-c`` protocol level,10to control the naming.11 12For brevity this document refers to ``name`` properties of various13objects by the object type. For example ``$attr`` is the value14of ``name`` in an attribute, and ``$family`` is the name of the15family (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 literal19``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 is25appended (``do`` -> ``do_``).26 27Globals28=======29 30``c-family-name`` controls the name of the ``#define`` for the family31name, default is ``$family-FAMILY-NAME``.32 33``c-version-name`` controls the name of the ``#define`` for the version34of the family, default is ``$family-FAMILY-VERSION``.35 36``max-by-define`` selects if max values for enums are defined as a37``#define`` rather than inside the enum.38 39Definitions40===========41 42Constants43---------44 45Every constant is rendered as a ``#define``.46The name of the constant is ``$family-$constant`` and the value47is rendered as a string or integer according to its type in the spec.48 49Enums and flags50---------------51 52Enums are named ``$family-$enum``. The full name can be set directly53or suppressed by specifying the ``enum-name`` property.54Default entry name is ``$family-$enum-$entry``.55If ``name-prefix`` is specified it replaces the ``$family-$enum``56portion of the entry name.57 58Boolean ``render-max`` controls creation of the max values59(which are enabled by default for attribute enums).60 61Attributes62==========63 64Each attribute set (excluding fractional sets) is rendered as an enum.65 66Attribute enums are traditionally unnamed in netlink headers.67If naming is desired ``enum-name`` can be used to specify the name.68 69The default attribute name prefix is ``$family-A`` if the name of the set70is the same as the name of the family and ``$family-A-$set`` if the names71differ. 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 ``$pfx-MAX``77which are used for sizing attribute tables.78These two names can be specified directly with the ``attr-cnt-name``79and ``attr-max-name`` properties respectively.80 81If ``max-by-define`` is set to ``true`` at the global level ``attr-max-name``82will be specified as a ``#define`` rather than an enum value.83 84Operations85==========86 87Operations are named ``$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 max92attributes. For operations those attributes can be renamed with93``cmd-cnt-name`` and ``cmd-max-name``. Max will be a define if ``max-by-define``94is ``true``.95 96Multicast groups97================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 overwritten101with the ``c-define-name`` property.102 103Code generation104===============105 106uAPI header is assumed to come from ``<linux/$family.h>`` in the default header107search path. It can be changed using the ``uapi-header`` global property.108