.. Permission is granted to copy, distribute and/or modify this
.. document under the terms of the GNU Free Documentation License,
.. Version 1.1 or any later version published by the Free Software
.. Foundation, with no Invariant Sections, no Front-Cover Texts
.. and no Back-Cover Texts. A copy of the license is included at
.. Documentation/media/uapi/fdl-appendix.rst.
..
.. TODO: replace it to GFDL-1.1-or-later WITH no-invariant-sections

.. _func-munmap:

*************
V4L2 munmap()
*************

Name
====

v4l2-munmap - Unmap device memory


Synopsis
========

.. code-block:: c

    #include <unistd.h>
    #include <sys/mman.h>


.. c:function:: int munmap( void *start, size_t length )
    :name: v4l2-munmap

Arguments
=========

``start``
    Address of the mapped buffer as returned by the
    :ref:`mmap() <func-mmap>` function.

``length``
    Length of the mapped buffer. This must be the same value as given to
    :ref:`mmap() <func-mmap>` and returned by the driver in the struct
    :c:type:`v4l2_buffer` ``length`` field for the
    single-planar API and in the struct
    :c:type:`v4l2_plane` ``length`` field for the
    multi-planar API.


Description
===========

Unmaps a previously with the :ref:`mmap() <func-mmap>` function mapped
buffer and frees it, if possible.


Return Value
============

On success :ref:`munmap() <func-munmap>` returns 0, on failure -1 and the
``errno`` variable is set appropriately:

EINVAL
    The ``start`` or ``length`` is incorrect, or no buffers have been
    mapped yet.