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author | Daniel Baumann <daniel.baumann@progress-linux.org> | 2024-04-27 10:05:51 +0000 |
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committer | Daniel Baumann <daniel.baumann@progress-linux.org> | 2024-04-27 10:05:51 +0000 |
commit | 5d1646d90e1f2cceb9f0828f4b28318cd0ec7744 (patch) | |
tree | a94efe259b9009378be6d90eb30d2b019d95c194 /Documentation/userspace-api/media/v4l/func-write.rst | |
parent | Initial commit. (diff) | |
download | linux-430c2fc249ea5c0536abd21c23382884005c9093.tar.xz linux-430c2fc249ea5c0536abd21c23382884005c9093.zip |
Adding upstream version 5.10.209.upstream/5.10.209upstream
Signed-off-by: Daniel Baumann <daniel.baumann@progress-linux.org>
Diffstat (limited to 'Documentation/userspace-api/media/v4l/func-write.rst')
-rw-r--r-- | Documentation/userspace-api/media/v4l/func-write.rst | 81 |
1 files changed, 81 insertions, 0 deletions
diff --git a/Documentation/userspace-api/media/v4l/func-write.rst b/Documentation/userspace-api/media/v4l/func-write.rst new file mode 100644 index 000000000..49f5a0f42 --- /dev/null +++ b/Documentation/userspace-api/media/v4l/func-write.rst @@ -0,0 +1,81 @@ +.. SPDX-License-Identifier: GFDL-1.1-no-invariants-or-later +.. c:namespace:: V4L + +.. _func-write: + +************ +V4L2 write() +************ + +Name +==== + +v4l2-write - Write to a V4L2 device + +Synopsis +======== + +.. code-block:: c + + #include <unistd.h> + +.. c:function:: ssize_t write( int fd, void *buf, size_t count ) + +Arguments +========= + +``fd`` + File descriptor returned by :c:func:`open()`. + +``buf`` + Buffer with data to be written + +``count`` + Number of bytes at the buffer + +Description +=========== + +:c:func:`write()` writes up to ``count`` bytes to the device +referenced by the file descriptor ``fd`` from the buffer starting at +``buf``. When the hardware outputs are not active yet, this function +enables them. When ``count`` is zero, :c:func:`write()` returns 0 +without any other effect. + +When the application does not provide more data in time, the previous +video frame, raw VBI image, sliced VPS or WSS data is displayed again. +Sliced Teletext or Closed Caption data is not repeated, the driver +inserts a blank line instead. + +Return Value +============ + +On success, the number of bytes written are returned. Zero indicates +nothing was written. On error, -1 is returned, and the ``errno`` +variable is set appropriately. In this case the next write will start at +the beginning of a new frame. Possible error codes are: + +EAGAIN + Non-blocking I/O has been selected using the + :ref:`O_NONBLOCK <func-open>` flag and no buffer space was + available to write the data immediately. + +EBADF + ``fd`` is not a valid file descriptor or is not open for writing. + +EBUSY + The driver does not support multiple write streams and the device is + already in use. + +EFAULT + ``buf`` references an inaccessible memory area. + +EINTR + The call was interrupted by a signal before any data was written. + +EIO + I/O error. This indicates some hardware problem. + +EINVAL + The :c:func:`write()` function is not supported by this driver, + not on this device, or generally not on this type of device. |