.. 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

.. _dmx_fread:

=======================
Digital TV demux read()
=======================

Name
----

Digital TV demux read()


Synopsis
--------

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

Arguments
---------

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

 ``buf``
   Buffer to be filled

``count``
   Max number of bytes to read

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

This system call returns filtered data, which might be section or Packetized
Elementary Stream (PES) data. The filtered data is transferred from
the driver’s internal circular buffer to ``buf``. The maximum amount of data
to be transferred is implied by count.

.. note::

   if a section filter created with
   :c:type:`DMX_CHECK_CRC <dmx_sct_filter_params>` flag set,
   data that fails on CRC check will be silently ignored.


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

On success 0 is returned.

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

.. tabularcolumns:: |p{2.5cm}|p{15.0cm}|

.. flat-table::
    :header-rows:  0
    :stub-columns: 0
    :widths: 1 16

    -  -  ``EWOULDBLOCK``
       -  No data to return and ``O_NONBLOCK`` was specified.

    -  -  ``EOVERFLOW``
       -  The filtered data was not read from the buffer in due time,
	  resulting in non-read data being lost. The buffer is flushed.

    -  -  ``ETIMEDOUT``
       -  The section was not loaded within the stated timeout period.
          See ioctl :ref:`DMX_SET_FILTER` for how to set a timeout.

    -  -  ``EFAULT``
       -  The driver failed to write to the callers buffer due to an
          invalid \*buf pointer.


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