Documentation/userspace-api/media/dvb/dmx-fopen.rst

.. SPDX-License-Identifier: GFDL-1.1-no-invariants-or-later
.. c:namespace:: DTV.dmx

.. _dmx_fopen:

=======================
Digital TV demux open()
=======================

Name
----

Digital TV demux open()

Synopsis
--------

.. c:function:: int open(const char *deviceName, int flags)

Arguments
---------

``name``
  Name of specific Digital TV demux device.

``flags``
  A bit-wise OR of the following flags:

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    -
       - ``O_RDONLY``
       - read-only access

    -
       - ``O_RDWR``
       - read/write access

    -
       - ``O_NONBLOCK``
       - open in non-blocking mode
         (blocking mode is the default)

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

This system call, used with a device name of ``/dev/dvb/adapter?/demux?``,
allocates a new filter and returns a handle which can be used for
subsequent control of that filter. This call has to be made for each
filter to be used, i.e. every returned file descriptor is a reference to
a single filter. ``/dev/dvb/adapter?/dvr?`` is a logical device to be used
for retrieving Transport Streams for digital video recording. When
reading from this device a transport stream containing the packets from
all PES filters set in the corresponding demux device
(``/dev/dvb/adapter?/demux?``) having the output set to ``DMX_OUT_TS_TAP``.
A recorded Transport Stream is replayed by writing to this device.

The significance of blocking or non-blocking mode is described in the
documentation for functions where there is a difference. It does not
affect the semantics of the ``open()`` call itself. A device opened
in blocking mode can later be put into non-blocking mode (and vice versa)
using the ``F_SETFL`` command of the fcntl system call.

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

On success 0 is returned.

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

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    -  -  ``EMFILE``
       -  “Too many open files”, i.e. no more filters available.

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