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+.. SPDX-License-Identifier: GFDL-1.1-no-invariants-or-later
+.. c:namespace:: DTV.dmx
+
+.. _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)
+
+Arguments
+---------
+
+``fd``
+  File descriptor returned by a previous call to :c:func:`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.
+
+.. tabularcolumns:: |p{2.5cm}|p{15.0cm}|
+
+.. flat-table::
+    :header-rows:  0
+    :stub-columns: 0
+    :widths: 1 16
+
+    -  -  ``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.