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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/vidioc-subdev-g-frame-interval.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/vidioc-subdev-g-frame-interval.rst')
-rw-r--r-- | Documentation/userspace-api/media/v4l/vidioc-subdev-g-frame-interval.rst | 119 |
1 files changed, 119 insertions, 0 deletions
diff --git a/Documentation/userspace-api/media/v4l/vidioc-subdev-g-frame-interval.rst b/Documentation/userspace-api/media/v4l/vidioc-subdev-g-frame-interval.rst new file mode 100644 index 000000000..3a50f8b28 --- /dev/null +++ b/Documentation/userspace-api/media/v4l/vidioc-subdev-g-frame-interval.rst @@ -0,0 +1,119 @@ +.. SPDX-License-Identifier: GFDL-1.1-no-invariants-or-later +.. c:namespace:: V4L + +.. _VIDIOC_SUBDEV_G_FRAME_INTERVAL: + +******************************************************************** +ioctl VIDIOC_SUBDEV_G_FRAME_INTERVAL, VIDIOC_SUBDEV_S_FRAME_INTERVAL +******************************************************************** + +Name +==== + +VIDIOC_SUBDEV_G_FRAME_INTERVAL - VIDIOC_SUBDEV_S_FRAME_INTERVAL - Get or set the frame interval on a subdev pad + +Synopsis +======== + +.. c:macro:: VIDIOC_SUBDEV_G_FRAME_INTERVAL + +``int ioctl(int fd, VIDIOC_SUBDEV_G_FRAME_INTERVAL, struct v4l2_subdev_frame_interval *argp)`` + +.. c:macro:: VIDIOC_SUBDEV_S_FRAME_INTERVAL + +``int ioctl(int fd, VIDIOC_SUBDEV_S_FRAME_INTERVAL, struct v4l2_subdev_frame_interval *argp)`` + +Arguments +========= + +``fd`` + File descriptor returned by :c:func:`open()`. + +``argp`` + Pointer to struct :c:type:`v4l2_subdev_frame_interval`. + +Description +=========== + +These ioctls are used to get and set the frame interval at specific +subdev pads in the image pipeline. The frame interval only makes sense +for sub-devices that can control the frame period on their own. This +includes, for instance, image sensors and TV tuners. Sub-devices that +don't support frame intervals must not implement these ioctls. + +To retrieve the current frame interval applications set the ``pad`` +field of a struct +:c:type:`v4l2_subdev_frame_interval` to +the desired pad number as reported by the media controller API. When +they call the ``VIDIOC_SUBDEV_G_FRAME_INTERVAL`` ioctl with a pointer to +this structure the driver fills the members of the ``interval`` field. + +To change the current frame interval applications set both the ``pad`` +field and all members of the ``interval`` field. When they call the +``VIDIOC_SUBDEV_S_FRAME_INTERVAL`` ioctl with a pointer to this +structure the driver verifies the requested interval, adjusts it based +on the hardware capabilities and configures the device. Upon return the +struct +:c:type:`v4l2_subdev_frame_interval` +contains the current frame interval as would be returned by a +``VIDIOC_SUBDEV_G_FRAME_INTERVAL`` call. + +Calling ``VIDIOC_SUBDEV_S_FRAME_INTERVAL`` on a subdev device node that has been +registered in read-only mode is not allowed. An error is returned and the errno +variable is set to ``-EPERM``. + +Drivers must not return an error solely because the requested interval +doesn't match the device capabilities. They must instead modify the +interval to match what the hardware can provide. The modified interval +should be as close as possible to the original request. + +Changing the frame interval shall never change the format. Changing the +format, on the other hand, may change the frame interval. + +Sub-devices that support the frame interval ioctls should implement them +on a single pad only. Their behaviour when supported on multiple pads of +the same sub-device is not defined. + +.. c:type:: v4l2_subdev_frame_interval + +.. tabularcolumns:: |p{4.4cm}|p{4.4cm}|p{8.7cm}| + +.. flat-table:: struct v4l2_subdev_frame_interval + :header-rows: 0 + :stub-columns: 0 + :widths: 1 1 2 + + * - __u32 + - ``pad`` + - Pad number as reported by the media controller API. + * - struct :c:type:`v4l2_fract` + - ``interval`` + - Period, in seconds, between consecutive video frames. + * - __u32 + - ``reserved``\ [9] + - Reserved for future extensions. Applications and drivers must set + the array to zero. + +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. + +EBUSY + The frame interval can't be changed because the pad is currently + busy. This can be caused, for instance, by an active video stream on + the pad. The ioctl must not be retried without performing another + action to fix the problem first. Only returned by + ``VIDIOC_SUBDEV_S_FRAME_INTERVAL`` + +EINVAL + The struct + :c:type:`v4l2_subdev_frame_interval` + ``pad`` references a non-existing pad, or the pad doesn't support + frame intervals. + +EPERM + The ``VIDIOC_SUBDEV_S_FRAME_INTERVAL`` ioctl has been called on a read-only + subdevice. |