.. 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/userspace-api/media/fdl-appendix.rst.
..
.. TODO: replace it to GFDL-1.1-or-later WITH no-invariant-sections

.. _dmx_fwrite:

========================
Digital TV demux write()
========================

Name
----

Digital TV demux write()


Synopsis
--------

.. c:function:: ssize_t write(int fd, const void *buf, size_t count)
    :name: dvb-dmx-write

Arguments
---------

``fd``
  File descriptor returned by a previous call to :c:func:`open() <dvb-ca-open>`.

``buf``
     Buffer with data to be written

``count``
    Number of bytes at the buffer

Description
-----------

This system call is only provided by the logical device
``/dev/dvb/adapter?/dvr?``, associated with the physical demux device that
provides the actual DVR functionality. It is used for replay of a
digitally recorded Transport Stream. Matching filters have to be defined
in the corresponding physical demux device, ``/dev/dvb/adapter?/demux?``.
The amount of data to be transferred is implied by count.


Return Value
------------

On success 0 is returned.

On error -1 is returned, and the ``errno`` variable is set
appropriately.

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    -  -  ``EWOULDBLOCK``
       -  No data was written. This might happen if ``O_NONBLOCK`` was
	  specified and there is no more buffer space available (if
	  ``O_NONBLOCK`` is not specified the function will block until buffer
	  space is available).

    -  -  ``EBUSY``
       -  This error code indicates that there are conflicting requests. The
	  corresponding demux device is setup to receive data from the
	  front- end. Make sure that these filters are stopped and that the
	  filters with input set to ``DMX_IN_DVR`` are started.

The generic error codes are described at the
:ref:`Generic Error Codes <gen-errors>` chapter.