1 .. -*- coding: utf-8; mode: rst -*-
12 v4l2-write - Write to a V4L2 device
23 .. cpp:function:: ssize_t write( int fd, void *buf, size_t count )
30 File descriptor returned by :ref:`open() <func-open>`.
39 :ref:`write() <func-write>` writes up to ``count`` bytes to the device
40 referenced by the file descriptor ``fd`` from the buffer starting at
41 ``buf``. When the hardware outputs are not active yet, this function
42 enables them. When ``count`` is zero, :ref:`write() <func-write>` returns 0
43 without any other effect.
45 When the application does not provide more data in time, the previous
46 video frame, raw VBI image, sliced VPS or WSS data is displayed again.
47 Sliced Teletext or Closed Caption data is not repeated, the driver
48 inserts a blank line instead.
54 On success, the number of bytes written are returned. Zero indicates
55 nothing was written. On error, -1 is returned, and the ``errno``
56 variable is set appropriately. In this case the next write will start at
57 the beginning of a new frame. Possible error codes are:
60 Non-blocking I/O has been selected using the
61 :ref:`O_NONBLOCK <func-open>` flag and no buffer space was
62 available to write the data immediately.
65 ``fd`` is not a valid file descriptor or is not open for writing.
68 The driver does not support multiple write streams and the device is
72 ``buf`` references an inaccessible memory area.
75 The call was interrupted by a signal before any data was written.
78 I/O error. This indicates some hardware problem.
81 The :ref:`write() <func-write>` function is not supported by this driver,
82 not on this device, or generally not on this type of device.