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+.. -*- coding: utf-8; mode: rst -*-
+
+.. _VIDIOC_QUERYCAP:
+
+*********************
+ioctl VIDIOC_QUERYCAP
+*********************
+
+Name
+====
+
+VIDIOC_QUERYCAP - Query device capabilities
+
+
+Synopsis
+========
+
+.. cpp:function:: int ioctl( int fd, int request, struct v4l2_capability *argp )
+
+
+Arguments
+=========
+
+``fd``
+ File descriptor returned by :ref:`open() <func-open>`.
+
+``request``
+ VIDIOC_QUERYCAP
+
+``argp``
+
+
+Description
+===========
+
+All V4L2 devices support the ``VIDIOC_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 :ref:`v4l2_capability <v4l2-capability>` which is
+filled by the driver. When the driver is not compatible with this
+specification the ioctl returns an ``EINVAL`` error code.
+
+
+.. _v4l2-capability:
+
+.. flat-table:: struct v4l2_capability
+ :header-rows: 0
+ :stub-columns: 0
+ :widths: 1 1 2
+
+
+ - .. row 1
+
+ - __u8
+
+ - ``driver``\ [16]
+
+ - Name of the driver, a unique NUL-terminated ASCII string. For
+ example: "bttv". Driver specific applications can use this
+ information to verify the driver identity. It is also useful to
+ work around known bugs, or to identify drivers in error reports.
+
+ Storing strings in fixed sized arrays is bad practice but
+ unavoidable here. Drivers and applications should take precautions
+ to never read or write beyond the end of the array and to make
+ sure the strings are properly NUL-terminated.
+
+ - .. row 2
+
+ - __u8
+
+ - ``card``\ [32]
+
+ - Name of the device, a NUL-terminated UTF-8 string. For example:
+ "Yoyodyne TV/FM". One driver may support different brands or
+ models of video hardware. This information is intended for users,
+ for example in a menu of available devices. Since multiple TV
+ cards of the same brand may be installed which are supported by
+ the same driver, this name should be combined with the character
+ device file name (e. g. ``/dev/video2``) or the ``bus_info``
+ string to avoid ambiguities.
+
+ - .. row 3
+
+ - __u8
+
+ - ``bus_info``\ [32]
+
+ - Location of the device in the system, a NUL-terminated ASCII
+ string. For example: "PCI:0000:05:06.0". This information is
+ intended for users, to distinguish multiple identical devices. If
+ no such information is available the field must simply count the
+ devices controlled by the driver ("platform:vivi-000"). The
+ bus_info must start with "PCI:" for PCI boards, "PCIe:" for PCI
+ Express boards, "usb-" for USB devices, "I2C:" for i2c devices,
+ "ISA:" for ISA devices, "parport" for parallel port devices and
+ "platform:" for platform devices.
+
+ - .. row 4
+
+ - __u32
+
+ - ``version``
+
+ - Version number of the driver.
+
+ Starting with kernel 3.1, 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:
+
+ - .. row 5
+
+ - :cspan:`2`
+
+
+ .. code-block:: c
+
+ #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);
+
+ - .. row 6
+
+ - __u32
+
+ - ``capabilities``
+
+ - Available capabilities of the physical device as a whole, see
+ :ref:`device-capabilities`. The same physical device can export
+ multiple devices in /dev (e.g. /dev/videoX, /dev/vbiY and
+ /dev/radioZ). The ``capabilities`` field should contain a union of
+ all capabilities available around the several V4L2 devices
+ exported to userspace. For all those devices the ``capabilities``
+ field returns the same set of capabilities. This allows
+ applications to open just one of the devices (typically the video
+ device) and discover whether video, vbi and/or radio are also
+ supported.
+
+ - .. row 7
+
+ - __u32
+
+ - ``device_caps``
+
+ - Device capabilities of the opened device, see
+ :ref:`device-capabilities`. Should contain the available
+ capabilities of that specific device node. So, for example,
+ ``device_caps`` of a radio device will only contain radio related
+ capabilities and no video or vbi capabilities. This field is only
+ set if the ``capabilities`` field contains the
+ ``V4L2_CAP_DEVICE_CAPS`` capability. Only the ``capabilities``
+ field can have the ``V4L2_CAP_DEVICE_CAPS`` capability,
+ ``device_caps`` will never set ``V4L2_CAP_DEVICE_CAPS``.
+
+ - .. row 8
+
+ - __u32
+
+ - ``reserved``\ [3]
+
+ - Reserved for future extensions. Drivers must set this array to
+ zero.
+
+
+
+.. _device-capabilities:
+
+.. flat-table:: Device Capabilities Flags
+ :header-rows: 0
+ :stub-columns: 0
+ :widths: 3 1 4
+
+
+ - .. row 1
+
+ - ``V4L2_CAP_VIDEO_CAPTURE``
+
+ - 0x00000001
+
+ - The device supports the single-planar API through the
+ :ref:`Video Capture <capture>` interface.
+
+ - .. row 2
+
+ - ``V4L2_CAP_VIDEO_CAPTURE_MPLANE``
+
+ - 0x00001000
+
+ - The device supports the :ref:`multi-planar API <planar-apis>`
+ through the :ref:`Video Capture <capture>` interface.
+
+ - .. row 3
+
+ - ``V4L2_CAP_VIDEO_OUTPUT``
+
+ - 0x00000002
+
+ - The device supports the single-planar API through the
+ :ref:`Video Output <output>` interface.
+
+ - .. row 4
+
+ - ``V4L2_CAP_VIDEO_OUTPUT_MPLANE``
+
+ - 0x00002000
+
+ - The device supports the :ref:`multi-planar API <planar-apis>`
+ through the :ref:`Video Output <output>` interface.
+
+ - .. row 5
+
+ - ``V4L2_CAP_VIDEO_M2M``
+
+ - 0x00004000
+
+ - The device supports the single-planar API through the Video
+ Memory-To-Memory interface.
+
+ - .. row 6
+
+ - ``V4L2_CAP_VIDEO_M2M_MPLANE``
+
+ - 0x00008000
+
+ - The device supports the :ref:`multi-planar API <planar-apis>`
+ through the Video Memory-To-Memory interface.
+
+ - .. row 7
+
+ - ``V4L2_CAP_VIDEO_OVERLAY``
+
+ - 0x00000004
+
+ - The device supports the :ref:`Video Overlay <overlay>`
+ interface. A video overlay device typically stores captured images
+ directly in the video memory of a graphics card, with hardware
+ clipping and scaling.
+
+ - .. row 8
+
+ - ``V4L2_CAP_VBI_CAPTURE``
+
+ - 0x00000010
+
+ - The device supports the :ref:`Raw VBI Capture <raw-vbi>`
+ interface, providing Teletext and Closed Caption data.
+
+ - .. row 9
+
+ - ``V4L2_CAP_VBI_OUTPUT``
+
+ - 0x00000020
+
+ - The device supports the :ref:`Raw VBI Output <raw-vbi>`
+ interface.
+
+ - .. row 10
+
+ - ``V4L2_CAP_SLICED_VBI_CAPTURE``
+
+ - 0x00000040
+
+ - The device supports the :ref:`Sliced VBI Capture <sliced>`
+ interface.
+
+ - .. row 11
+
+ - ``V4L2_CAP_SLICED_VBI_OUTPUT``
+
+ - 0x00000080
+
+ - The device supports the :ref:`Sliced VBI Output <sliced>`
+ interface.
+
+ - .. row 12
+
+ - ``V4L2_CAP_RDS_CAPTURE``
+
+ - 0x00000100
+
+ - The device supports the :ref:`RDS <rds>` capture interface.
+
+ - .. row 13
+
+ - ``V4L2_CAP_VIDEO_OUTPUT_OVERLAY``
+
+ - 0x00000200
+
+ - The device supports the :ref:`Video Output Overlay <osd>` (OSD)
+ interface. Unlike the *Video Overlay* interface, this is a
+ secondary function of video output devices and overlays an image
+ onto an outgoing video signal. When the driver sets this flag, it
+ must clear the ``V4L2_CAP_VIDEO_OVERLAY`` flag and vice
+ versa. [#f1]_
+
+ - .. row 14
+
+ - ``V4L2_CAP_HW_FREQ_SEEK``
+
+ - 0x00000400
+
+ - The device supports the
+ :ref:`VIDIOC_S_HW_FREQ_SEEK` ioctl
+ for hardware frequency seeking.
+
+ - .. row 15
+
+ - ``V4L2_CAP_RDS_OUTPUT``
+
+ - 0x00000800
+
+ - The device supports the :ref:`RDS <rds>` output interface.
+
+ - .. row 16
+
+ - ``V4L2_CAP_TUNER``
+
+ - 0x00010000
+
+ - The device has some sort of tuner to receive RF-modulated video
+ signals. For more information about tuner programming see
+ :ref:`tuner`.
+
+ - .. row 17
+
+ - ``V4L2_CAP_AUDIO``
+
+ - 0x00020000
+
+ - The device has audio inputs or outputs. It may or may not support
+ audio recording or playback, in PCM or compressed formats. PCM
+ audio support must be implemented as ALSA or OSS interface. For
+ more information on audio inputs and outputs see :ref:`audio`.
+
+ - .. row 18
+
+ - ``V4L2_CAP_RADIO``
+
+ - 0x00040000
+
+ - This is a radio receiver.
+
+ - .. row 19
+
+ - ``V4L2_CAP_MODULATOR``
+
+ - 0x00080000
+
+ - The device has some sort of modulator to emit RF-modulated
+ video/audio signals. For more information about modulator
+ programming see :ref:`tuner`.
+
+ - .. row 20
+
+ - ``V4L2_CAP_SDR_CAPTURE``
+
+ - 0x00100000
+
+ - The device supports the :ref:`SDR Capture <sdr>` interface.
+
+ - .. row 21
+
+ - ``V4L2_CAP_EXT_PIX_FORMAT``
+
+ - 0x00200000
+
+ - The device supports the struct
+ :ref:`v4l2_pix_format <v4l2-pix-format>` extended fields.
+
+ - .. row 22
+
+ - ``V4L2_CAP_SDR_OUTPUT``
+
+ - 0x00400000
+
+ - The device supports the :ref:`SDR Output <sdr>` interface.
+
+ - .. row 23
+
+ - ``V4L2_CAP_READWRITE``
+
+ - 0x01000000
+
+ - The device supports the :ref:`read() <rw>` and/or
+ :ref:`write() <rw>` I/O methods.
+
+ - .. row 24
+
+ - ``V4L2_CAP_ASYNCIO``
+
+ - 0x02000000
+
+ - The device supports the :ref:`asynchronous <async>` I/O methods.
+
+ - .. row 25
+
+ - ``V4L2_CAP_STREAMING``
+
+ - 0x04000000
+
+ - The device supports the :ref:`streaming <mmap>` I/O method.
+
+ - .. row 26
+
+ - ``V4L2_CAP_DEVICE_CAPS``
+
+ - 0x80000000
+
+ - The driver fills the ``device_caps`` field. This capability can
+ only appear in the ``capabilities`` field and never in the
+ ``device_caps`` field.
+
+
+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.
+
+.. [#f1]
+ The struct :ref:`v4l2_framebuffer <v4l2-framebuffer>` lacks an
+ enum :ref:`v4l2_buf_type <v4l2-buf-type>` field, therefore the
+ type of overlay is implied by the driver capabilities.
generated by cgit v1.2.3-54-g00ecf (git 2.45.2) at 2024-11-03 22:50:22 +0000