.. SPDX-License-Identifier: BSD-3-Clause ==============================Netlink spec C code generation============================== This document describes how Netlink specifications are used to renderC code (uAPI, policies etc.). It also defines the additional propertiesallowed in older families by the ``genetlink-c`` protocol level,to control the naming. For brevity this document refers to ``name`` properties of variousobjects by the object type. For example ``$attr`` is the valueof ``name`` in an attribute, and ``$family`` is the name of thefamily (the global ``name`` property). The upper case is used to denote literal values, e.g. ``$family-CMD``means the concatenation of ``$family``, a dash character, and the literal``CMD``. The names of ``#defines`` and enum values are always converted to upper case,and with dashes (``-``) replaced by underscores (``_``). If the constructed name is a C keyword, an extra underscore isappended (``do`` -> ``do_``). Globals======= ``c-family-name`` controls the name of the ``#define`` for the familyname, default is ``$family-FAMILY-NAME``. ``c-version-name`` controls the name of the ``#define`` for the versionof the family, default is ``$family-FAMILY-VERSION``. ``max-by-define`` selects if max values for enums are defined as a``#define`` rather than inside the enum. Definitions=========== Constants--------- Every constant is rendered as a ``#define``.The name of the constant is ``$family-$constant`` and the valueis rendered as a string or integer according to its type in the spec. Enums and flags--------------- Enums are named ``$family-$enum``. The full name can be set directlyor suppressed by specifying the ``enum-name`` property.Default entry name is ``$family-$enum-$entry``.If ``name-prefix`` is specified it replaces the ``$family-$enum``portion of the entry name. Boolean ``render-max`` controls creation of the max values(which are enabled by default for attribute enums). These maxvalues are named ``__$pfx-MAX`` and ``$pfx-MAX``. The nameof the first value can be overridden via ``enum-cnt-name`` property. Attributes========== Each attribute set (excluding fractional sets) is rendered as an enum. Attribute enums are traditionally unnamed in netlink headers.If naming is desired ``enum-name`` can be used to specify the name. The default attribute name prefix is ``$family-A`` if the name of the setis the same as the name of the family and ``$family-A-$set`` if the namesdiffer. The prefix can be overridden by the ``name-prefix`` property of a set.The rest of the section will refer to the prefix as ``$pfx``. Attributes are named ``$pfx-$attribute``. Attribute enums end with two special values ``__$pfx-MAX`` and ``$pfx-MAX``which are used for sizing attribute tables.These two names can be specified directly with the ``attr-cnt-name``and ``attr-max-name`` properties respectively. If ``max-by-define`` is set to ``true`` at the global level ``attr-max-name``will be specified as a ``#define`` rather than an enum value. Operations========== Operations are named ``$family-CMD-$operation``.If ``name-prefix`` is specified it replaces the ``$family-CMD``portion of the name. Similarly to attribute enums operation enums end with special count and maxattributes. For operations those attributes can be renamed with``cmd-cnt-name`` and ``cmd-max-name``. Max will be a define if ``max-by-define``is ``true``. Multicast groups================ Each multicast group gets a define rendered into the kernel uAPI header.The name of the define is ``$family-MCGRP-$group``, and can be overwrittenwith the ``c-define-name`` property. Code generation=============== uAPI header is assumed to come from ``<linux/$family.h>`` in the default headersearch path. It can be changed using the ``uapi-header`` global property.