summaryrefslogtreecommitdiffstats
path: root/Documentation/userspace-api/media/v4l/vidioc-querystd.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/vidioc-querystd.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/vidioc-querystd.rst')
-rw-r--r--Documentation/userspace-api/media/v4l/vidioc-querystd.rst69
1 files changed, 69 insertions, 0 deletions
diff --git a/Documentation/userspace-api/media/v4l/vidioc-querystd.rst b/Documentation/userspace-api/media/v4l/vidioc-querystd.rst
new file mode 100644
index 000000000..4a88287d8
--- /dev/null
+++ b/Documentation/userspace-api/media/v4l/vidioc-querystd.rst
@@ -0,0 +1,69 @@
+.. SPDX-License-Identifier: GFDL-1.1-no-invariants-or-later
+.. c:namespace:: V4L
+
+.. _VIDIOC_QUERYSTD:
+
+*********************************************
+ioctl VIDIOC_QUERYSTD, VIDIOC_SUBDEV_QUERYSTD
+*********************************************
+
+Name
+====
+
+VIDIOC_QUERYSTD - VIDIOC_SUBDEV_QUERYSTD - Sense the video standard received by the current input
+
+Synopsis
+========
+
+.. c:macro:: VIDIOC_QUERYSTD
+
+``int ioctl(int fd, VIDIOC_QUERYSTD, v4l2_std_id *argp)``
+
+.. c:macro:: VIDIOC_SUBDEV_QUERYSTD
+
+``int ioctl(int fd, VIDIOC_SUBDEV_QUERYSTD, v4l2_std_id *argp)``
+
+Arguments
+=========
+
+``fd``
+ File descriptor returned by :c:func:`open()`.
+
+``argp``
+ Pointer to :c:type:`v4l2_std_id`.
+
+Description
+===========
+
+The hardware may be able to detect the current video standard
+automatically. To do so, applications call :ref:`VIDIOC_QUERYSTD` with a
+pointer to a :ref:`v4l2_std_id <v4l2-std-id>` type. The driver
+stores here a set of candidates, this can be a single flag or a set of
+supported standards if for example the hardware can only distinguish
+between 50 and 60 Hz systems. If no signal was detected, then the driver
+will return V4L2_STD_UNKNOWN. When detection is not possible or fails,
+the set must contain all standards supported by the current video input
+or output.
+
+.. note::
+
+ Drivers shall *not* switch the video standard
+ automatically if a new video standard is detected. Instead, drivers
+ should send the ``V4L2_EVENT_SOURCE_CHANGE`` event (if they support
+ this) and expect that userspace will take action by calling
+ :ref:`VIDIOC_QUERYSTD`. The reason is that a new video standard can mean
+ different buffer sizes as well, and you cannot change buffer sizes on
+ the fly. In general, applications that receive the Source Change event
+ will have to call :ref:`VIDIOC_QUERYSTD`, and if the detected video
+ standard is valid they will have to stop streaming, set the new
+ standard, allocate new buffers and start streaming again.
+
+Return Value
+============
+
+On success 0 is returned, on error -1 and the ``errno`` variable is set
+appropriately. The generic error codes are described at the
+:ref:`Generic Error Codes <gen-errors>` chapter.
+
+ENODATA
+ Standard video timings are not supported for this input or output.