summaryrefslogtreecommitdiffstats
path: root/Documentation/userspace-api/media/v4l/func-write.rst
diff options
context:
space:
mode:
authorDaniel Baumann <daniel.baumann@progress-linux.org>2024-04-07 18:49:45 +0000
committerDaniel Baumann <daniel.baumann@progress-linux.org>2024-04-07 18:49:45 +0000
commit2c3c1048746a4622d8c89a29670120dc8fab93c4 (patch)
tree848558de17fb3008cdf4d861b01ac7781903ce39 /Documentation/userspace-api/media/v4l/func-write.rst
parentInitial commit. (diff)
downloadlinux-2c3c1048746a4622d8c89a29670120dc8fab93c4.tar.xz
linux-2c3c1048746a4622d8c89a29670120dc8fab93c4.zip
Adding upstream version 6.1.76.upstream/6.1.76
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.rst81
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.