Lines Matching refs:read
3 .. _func-read:
6 V4L2 read()
12 v4l2-read - Read from a V4L2 device
23 .. c:function:: ssize_t read( int fd, void *buf, size_t count )
24 :name: v4l2-read
36 Max number of bytes to read
41 :ref:`read() <func-read>` attempts to read up to ``count`` bytes from file
44 section, see ##. If ``count`` is zero, :ref:`read() <func-read>` returns zero
47 :ref:`read() <func-read>` call will provide at most one frame (two fields)
50 By default :ref:`read() <func-read>` blocks until data becomes available. When
56 :ref:`read() <func-read>` function must also support :ref:`select() <func-select>` and
59 Drivers can implement read functionality in different ways, using a
63 :ref:`read() <func-read>` never returns a "snapshot" of a buffer being filled.
65 application starts reading the buffer until the read is finished. Thus
70 The behavior of :ref:`read() <func-read>` when called during the active picture
74 previously, not read frame, and returns the frame being received at the
75 time of the :ref:`read() <func-read>` call as soon as it is complete.
78 :ref:`read() <func-read>` call. The frame being received at :ref:`read() <func-read>`
81 nominal frame rate. An example of this model is the video read mode of
82 the bttv driver, initiating a DMA to user memory when :ref:`read() <func-read>`
101 On success, the number of bytes read is returned. It is not an error if
104 :ref:`read() <func-read>` was interrupted by a signal. On error, -1 is
106 the next read will start at the beginning of a new frame. Possible error
118 The driver does not support multiple read streams and the device is
125 The call was interrupted by a signal before any data was read.
132 The :ref:`read() <func-read>` function is not supported by this driver, not