vidioc-subdev-querycap.rst

  1.. SPDX-License-Identifier: GFDL-1.1-no-invariants-or-later
  2.. c:namespace:: V4L
  3
  4.. _VIDIOC_SUBDEV_QUERYCAP:
  5
  6****************************
  7ioctl VIDIOC_SUBDEV_QUERYCAP
  8****************************
  9
 10Name
 11====
 12
 13VIDIOC_SUBDEV_QUERYCAP - Query sub-device capabilities
 14
 15Synopsis
 16========
 17
 18.. c:macro:: VIDIOC_SUBDEV_QUERYCAP
 19
 20``int ioctl(int fd, VIDIOC_SUBDEV_QUERYCAP, struct v4l2_subdev_capability *argp)``
 21
 22Arguments
 23=========
 24
 25``fd``
 26    File descriptor returned by :c:func:`open()`.
 27
 28``argp``
 29    Pointer to struct :c:type:`v4l2_subdev_capability`.
 30
 31Description
 32===========
 33
 34All V4L2 sub-devices support the ``VIDIOC_SUBDEV_QUERYCAP`` ioctl. It is used to
 35identify kernel devices compatible with this specification and to obtain
 36information about driver and hardware capabilities. The ioctl takes a pointer to
 37a struct :c:type:`v4l2_subdev_capability` which is filled by the driver. When
 38the driver is not compatible with this specification the ioctl returns
 39``ENOTTY`` error code.
 40
 41.. tabularcolumns:: |p{1.5cm}|p{2.9cm}|p{12.9cm}|
 42
 43.. c:type:: v4l2_subdev_capability
 44
 45.. flat-table:: struct v4l2_subdev_capability
 46    :header-rows:  0
 47    :stub-columns: 0
 48    :widths:       3 4 20
 49
 50    * - __u32
 51      - ``version``
 52      - Version number of the driver.
 53
 54	The version reported is provided by the V4L2 subsystem following the
 55	kernel numbering scheme. However, it may not always return the same
 56	version as the kernel if, for example, a stable or
 57	distribution-modified kernel uses the V4L2 stack from a newer kernel.
 58
 59	The version number is formatted using the ``KERNEL_VERSION()``
 60	macro:
 61    * - :cspan:`2`
 62
 63	``#define KERNEL_VERSION(a,b,c) (((a) << 16) + ((b) << 8) + (c))``
 64
 65	``__u32 version = KERNEL_VERSION(0, 8, 1);``
 66
 67	``printf ("Version: %u.%u.%u\\n",``
 68
 69	``(version >> 16) & 0xFF, (version >> 8) & 0xFF, version & 0xFF);``
 70    * - __u32
 71      - ``capabilities``
 72      - Sub-device capabilities of the opened device, see
 73	:ref:`subdevice-capabilities`.
 74    * - __u32
 75      - ``reserved``\ [14]
 76      - Reserved for future extensions. Set to 0 by the V4L2 core.
 77
 78.. tabularcolumns:: |p{6.8cm}|p{2.4cm}|p{8.1cm}|
 79
 80.. _subdevice-capabilities:
 81
 82.. cssclass:: longtable
 83
 84.. flat-table:: Sub-Device Capabilities Flags
 85    :header-rows:  0
 86    :stub-columns: 0
 87    :widths:       3 1 4
 88
 89    * - V4L2_SUBDEV_CAP_RO_SUBDEV
 90      - 0x00000001
 91      - The sub-device device node is registered in read-only mode.
 92	Access to the sub-device ioctls that modify the device state is
 93	restricted. Refer to each individual subdevice ioctl documentation
 94	for a description of which restrictions apply to a read-only sub-device.
 95
 96Return Value
 97============
 98
 99On success 0 is returned, on error -1 and the ``errno`` variable is set
100appropriately. The generic error codes are described at the
101:ref:`Generic Error Codes <gen-errors>` chapter.
102
103ENOTTY
104    The device node is not a V4L2 sub-device.