| Olivier Deprez | 157378f | 2022-04-04 15:47:50 +0200 | [diff] [blame^] | 1 | .. SPDX-License-Identifier: GFDL-1.1-no-invariants-or-later |
| 2 | .. c:namespace:: V4L |
| 3 | |
| 4 | .. _VIDIOC_SUBDEV_QUERYCAP: |
| 5 | |
| 6 | **************************** |
| 7 | ioctl VIDIOC_SUBDEV_QUERYCAP |
| 8 | **************************** |
| 9 | |
| 10 | Name |
| 11 | ==== |
| 12 | |
| 13 | VIDIOC_SUBDEV_QUERYCAP - Query sub-device capabilities |
| 14 | |
| 15 | Synopsis |
| 16 | ======== |
| 17 | |
| 18 | .. c:macro:: VIDIOC_SUBDEV_QUERYCAP |
| 19 | |
| 20 | ``int ioctl(int fd, VIDIOC_SUBDEV_QUERYCAP, struct v4l2_subdev_capability *argp)`` |
| 21 | |
| 22 | Arguments |
| 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 | |
| 31 | Description |
| 32 | =========== |
| 33 | |
| 34 | All V4L2 sub-devices support the ``VIDIOC_SUBDEV_QUERYCAP`` ioctl. It is used to |
| 35 | identify kernel devices compatible with this specification and to obtain |
| 36 | information about driver and hardware capabilities. The ioctl takes a pointer to |
| 37 | a struct :c:type:`v4l2_subdev_capability` which is filled by the driver. When |
| 38 | the driver is not compatible with this specification the ioctl returns |
| 39 | ``ENOTTY`` error code. |
| 40 | |
| 41 | .. tabularcolumns:: |p{1.5cm}|p{2.5cm}|p{13cm}| |
| 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{6cm}|p{2.2cm}|p{8.8cm}| |
| 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 | |
| 96 | Return Value |
| 97 | ============ |
| 98 | |
| 99 | On success 0 is returned, on error -1 and the ``errno`` variable is set |
| 100 | appropriately. The generic error codes are described at the |
| 101 | :ref:`Generic Error Codes <gen-errors>` chapter. |
| 102 | |
| 103 | ENOTTY |
| 104 | The device node is not a V4L2 sub-device. |