Lines Matching full:read
10 .. _func-read:
13 V4L2 read()
19 v4l2-read - Read from a V4L2 device
30 .. c:function:: ssize_t read( int fd, void *buf, size_t count )
31 :name: v4l2-read
43 Max number of bytes to read
48 :ref:`read() <func-read>` attempts to read up to ``count`` bytes from file
51 section, see ##. If ``count`` is zero, :ref:`read() <func-read>` returns zero
54 :ref:`read() <func-read>` call will provide at most one frame (two fields)
57 By default :ref:`read() <func-read>` blocks until data becomes available. When
63 :ref:`read() <func-read>` function must also support :ref:`select() <func-select>` and
66 Drivers can implement read functionality in different ways, using a
70 :ref:`read() <func-read>` never returns a "snapshot" of a buffer being filled.
72 application starts reading the buffer until the read is finished. Thus
77 The behavior of :ref:`read() <func-read>` when called during the active picture
81 previously, not read frame, and returns the frame being received at the
82 time of the :ref:`read() <func-read>` call as soon as it is complete.
85 :ref:`read() <func-read>` call. The frame being received at :ref:`read() <func-read>`
88 nominal frame rate. An example of this model is the video read mode of
89 the bttv driver, initiating a DMA to user memory when :ref:`read() <func-read>`
108 On success, the number of bytes read is returned. It is not an error if
111 :ref:`read() <func-read>` was interrupted by a signal. On error, -1 is
113 the next read will start at the beginning of a new frame. Possible error
125 The driver does not support multiple read streams and the device is
132 The call was interrupted by a signal before any data was read.
139 The :ref:`read() <func-read>` function is not supported by this driver, not