Documentation/userspace-api/netlink/c-code-gen.rst

Source file repositories/reference/linux-study-clean/Documentation/userspace-api/netlink/c-code-gen.rst

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Documentation/userspace-api/netlink/c-code-gen.rst
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Repository support layer: documentation, build tooling, samples, user-space helper tools, generated initramfs support, licenses, and validation utilities.

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.. SPDX-License-Identifier: BSD-3-Clause

==============================
Netlink spec C code generation
==============================

This document describes how Netlink specifications are used to render
C code (uAPI, policies etc.). It also defines the additional properties
allowed in older families by the ``genetlink-c`` protocol level,
to control the naming.

For brevity this document refers to ``name`` properties of various
objects by the object type. For example ``$attr`` is the value
of ``name`` in an attribute, and ``$family`` is the name of the
family (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 is
appended (``do`` -> ``do_``).

Globals
=======

``c-family-name`` controls the name of the ``#define`` for the family
name, default is ``$family-FAMILY-NAME``.

``c-version-name`` controls the name of the ``#define`` for the version
of 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 value
is 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 directly
or 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 max
values are named ``__$pfx-MAX`` and ``$pfx-MAX``. The name
of 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.

Annotation

Implementation Notes