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| -rw-r--r-- | Documentation/userspace-api/media/v4l/vidioc-subdev-querycap.rst | 104 |
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diff --git a/Documentation/userspace-api/media/v4l/vidioc-subdev-querycap.rst b/Documentation/userspace-api/media/v4l/vidioc-subdev-querycap.rst new file mode 100644 index 000000000..9b8d8644e --- /dev/null +++ b/Documentation/userspace-api/media/v4l/vidioc-subdev-querycap.rst @@ -0,0 +1,104 @@ +.. SPDX-License-Identifier: GFDL-1.1-no-invariants-or-later +.. c:namespace:: V4L + +.. _VIDIOC_SUBDEV_QUERYCAP: + +**************************** +ioctl VIDIOC_SUBDEV_QUERYCAP +**************************** + +Name +==== + +VIDIOC_SUBDEV_QUERYCAP - Query sub-device capabilities + +Synopsis +======== + +.. c:macro:: VIDIOC_SUBDEV_QUERYCAP + +``int ioctl(int fd, VIDIOC_SUBDEV_QUERYCAP, struct v4l2_subdev_capability *argp)`` + +Arguments +========= + +``fd`` + File descriptor returned by :c:func:`open()`. + +``argp`` + Pointer to struct :c:type:`v4l2_subdev_capability`. + +Description +=========== + +All V4L2 sub-devices support the ``VIDIOC_SUBDEV_QUERYCAP`` ioctl. It is used to +identify kernel devices compatible with this specification and to obtain +information about driver and hardware capabilities. The ioctl takes a pointer to +a struct :c:type:`v4l2_subdev_capability` which is filled by the driver. When +the driver is not compatible with this specification the ioctl returns +``ENOTTY`` error code. + +.. tabularcolumns:: |p{1.5cm}|p{2.9cm}|p{12.9cm}| + +.. c:type:: v4l2_subdev_capability + +.. flat-table:: struct v4l2_subdev_capability + :header-rows: 0 + :stub-columns: 0 + :widths: 3 4 20 + + * - __u32 + - ``version`` + - Version number of the driver. + + The version reported is provided by the V4L2 subsystem following the + kernel numbering scheme. However, it may not always return the same + version as the kernel if, for example, a stable or + distribution-modified kernel uses the V4L2 stack from a newer kernel. + + The version number is formatted using the ``KERNEL_VERSION()`` + macro: + * - :cspan:`2` + + ``#define KERNEL_VERSION(a,b,c) (((a) << 16) + ((b) << 8) + (c))`` + + ``__u32 version = KERNEL_VERSION(0, 8, 1);`` + + ``printf ("Version: %u.%u.%u\\n",`` + + ``(version >> 16) & 0xFF, (version >> 8) & 0xFF, version & 0xFF);`` + * - __u32 + - ``capabilities`` + - Sub-device capabilities of the opened device, see + :ref:`subdevice-capabilities`. + * - __u32 + - ``reserved``\ [14] + - Reserved for future extensions. Set to 0 by the V4L2 core. + +.. tabularcolumns:: |p{6.8cm}|p{2.4cm}|p{8.1cm}| + +.. _subdevice-capabilities: + +.. cssclass:: longtable + +.. flat-table:: Sub-Device Capabilities Flags + :header-rows: 0 + :stub-columns: 0 + :widths: 3 1 4 + + * - V4L2_SUBDEV_CAP_RO_SUBDEV + - 0x00000001 + - The sub-device device node is registered in read-only mode. + Access to the sub-device ioctls that modify the device state is + restricted. Refer to each individual subdevice ioctl documentation + for a description of which restrictions apply to a read-only sub-device. + +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. + +ENOTTY + The device node is not a V4L2 sub-device. |