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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-g-ctrl.rst | |
parent | Initial commit. (diff) | |
download | linux-upstream/5.10.209.tar.xz linux-upstream/5.10.209.zip |
Adding upstream version 5.10.209.upstream/5.10.209upstream
Signed-off-by: Daniel Baumann <daniel.baumann@progress-linux.org>
Diffstat (limited to '')
-rw-r--r-- | Documentation/userspace-api/media/v4l/vidioc-g-ctrl.rst | 97 |
1 files changed, 97 insertions, 0 deletions
diff --git a/Documentation/userspace-api/media/v4l/vidioc-g-ctrl.rst b/Documentation/userspace-api/media/v4l/vidioc-g-ctrl.rst new file mode 100644 index 000000000..4f1bed53f --- /dev/null +++ b/Documentation/userspace-api/media/v4l/vidioc-g-ctrl.rst @@ -0,0 +1,97 @@ +.. SPDX-License-Identifier: GFDL-1.1-no-invariants-or-later +.. c:namespace:: V4L + +.. _VIDIOC_G_CTRL: + +********************************** +ioctl VIDIOC_G_CTRL, VIDIOC_S_CTRL +********************************** + +Name +==== + +VIDIOC_G_CTRL - VIDIOC_S_CTRL - Get or set the value of a control + +Synopsis +======== + +.. c:macro:: VIDIOC_G_CTRL + +``int ioctl(int fd, VIDIOC_G_CTRL, struct v4l2_control *argp)`` + +.. c:macro:: VIDIOC_S_CTRL + +``int ioctl(int fd, VIDIOC_S_CTRL, struct v4l2_control *argp)`` + +Arguments +========= + +``fd`` + File descriptor returned by :c:func:`open()`. + +``argp`` + Pointer to struct :c:type:`v4l2_control`. + +Description +=========== + +To get the current value of a control applications initialize the ``id`` +field of a struct :c:type:`v4l2_control` and call the +:ref:`VIDIOC_G_CTRL <VIDIOC_G_CTRL>` ioctl with a pointer to this structure. To change the +value of a control applications initialize the ``id`` and ``value`` +fields of a struct :c:type:`v4l2_control` and call the +:ref:`VIDIOC_S_CTRL <VIDIOC_G_CTRL>` ioctl. + +When the ``id`` is invalid drivers return an ``EINVAL`` error code. When the +``value`` is out of bounds drivers can choose to take the closest valid +value or return an ``ERANGE`` error code, whatever seems more appropriate. +However, :ref:`VIDIOC_S_CTRL <VIDIOC_G_CTRL>` is a write-only ioctl, it does not return the +actual new value. If the ``value`` is inappropriate for the control +(e.g. if it refers to an unsupported menu index of a menu control), then +EINVAL error code is returned as well. + +These ioctls work only with user controls. For other control classes the +:ref:`VIDIOC_G_EXT_CTRLS <VIDIOC_G_EXT_CTRLS>`, +:ref:`VIDIOC_S_EXT_CTRLS <VIDIOC_G_EXT_CTRLS>` or +:ref:`VIDIOC_TRY_EXT_CTRLS <VIDIOC_G_EXT_CTRLS>` must be used. + +.. c:type:: v4l2_control + +.. tabularcolumns:: |p{4.4cm}|p{4.4cm}|p{8.7cm}| + +.. flat-table:: struct v4l2_control + :header-rows: 0 + :stub-columns: 0 + :widths: 1 1 2 + + * - __u32 + - ``id`` + - Identifies the control, set by the application. + * - __s32 + - ``value`` + - New value or current value. + +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. + +EINVAL + The struct :c:type:`v4l2_control` ``id`` is invalid + or the ``value`` is inappropriate for the given control (i.e. if a + menu item is selected that is not supported by the driver according + to :ref:`VIDIOC_QUERYMENU <VIDIOC_QUERYCTRL>`). + +ERANGE + The struct :c:type:`v4l2_control` ``value`` is out of + bounds. + +EBUSY + The control is temporarily not changeable, possibly because another + applications took over control of the device function this control + belongs to. + +EACCES + Attempt to set a read-only control or to get a write-only control. |