105 lines
2.8 KiB
ReStructuredText
105 lines
2.8 KiB
ReStructuredText
.. SPDX-License-Identifier: GFDL-1.1-no-invariants-or-later
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.. c:namespace:: V4L
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.. _VIDIOC_SUBDEV_QUERYCAP:
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****************************
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ioctl VIDIOC_SUBDEV_QUERYCAP
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****************************
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Name
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====
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VIDIOC_SUBDEV_QUERYCAP - Query sub-device capabilities
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Synopsis
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========
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.. c:macro:: VIDIOC_SUBDEV_QUERYCAP
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``int ioctl(int fd, VIDIOC_SUBDEV_QUERYCAP, struct v4l2_subdev_capability *argp)``
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Arguments
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=========
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``fd``
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File descriptor returned by :c:func:`open()`.
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``argp``
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Pointer to struct :c:type:`v4l2_subdev_capability`.
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Description
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===========
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All V4L2 sub-devices support the ``VIDIOC_SUBDEV_QUERYCAP`` ioctl. It is used to
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identify kernel devices compatible with this specification and to obtain
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information about driver and hardware capabilities. The ioctl takes a pointer to
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a struct :c:type:`v4l2_subdev_capability` which is filled by the driver. When
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the driver is not compatible with this specification the ioctl returns
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``ENOTTY`` error code.
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.. tabularcolumns:: |p{1.5cm}|p{2.9cm}|p{12.9cm}|
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.. c:type:: v4l2_subdev_capability
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.. flat-table:: struct v4l2_subdev_capability
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:header-rows: 0
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:stub-columns: 0
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:widths: 3 4 20
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* - __u32
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- ``version``
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- Version number of the driver.
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The version reported is provided by the V4L2 subsystem following the
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kernel numbering scheme. However, it may not always return the same
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version as the kernel if, for example, a stable or
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distribution-modified kernel uses the V4L2 stack from a newer kernel.
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The version number is formatted using the ``KERNEL_VERSION()``
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macro:
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* - :cspan:`2`
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``#define KERNEL_VERSION(a,b,c) (((a) << 16) + ((b) << 8) + (c))``
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``__u32 version = KERNEL_VERSION(0, 8, 1);``
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``printf ("Version: %u.%u.%u\\n",``
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``(version >> 16) & 0xFF, (version >> 8) & 0xFF, version & 0xFF);``
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* - __u32
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- ``capabilities``
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- Sub-device capabilities of the opened device, see
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:ref:`subdevice-capabilities`.
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* - __u32
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- ``reserved``\ [14]
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- Reserved for future extensions. Set to 0 by the V4L2 core.
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.. tabularcolumns:: |p{6.8cm}|p{2.4cm}|p{8.1cm}|
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.. _subdevice-capabilities:
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.. cssclass:: longtable
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.. flat-table:: Sub-Device Capabilities Flags
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:header-rows: 0
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:stub-columns: 0
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:widths: 3 1 4
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* - V4L2_SUBDEV_CAP_RO_SUBDEV
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- 0x00000001
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- The sub-device device node is registered in read-only mode.
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Access to the sub-device ioctls that modify the device state is
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restricted. Refer to each individual subdevice ioctl documentation
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for a description of which restrictions apply to a read-only sub-device.
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Return Value
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============
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On success 0 is returned, on error -1 and the ``errno`` variable is set
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appropriately. The generic error codes are described at the
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:ref:`Generic Error Codes <gen-errors>` chapter.
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ENOTTY
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The device node is not a V4L2 sub-device.
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