mirror of
https://mirrors.bfsu.edu.cn/git/linux.git
synced 2024-11-30 15:44:13 +08:00
b75c1d85c3
On tests with Spinx 1.4, some tables are still writing text outside cells. Adjust those tables. PS.: As this was revisited several times, I suspect that this will only be fully fixed if we add tabularcolumns to all tables at the V4L2 part of the book. Signed-off-by: Mauro Carvalho Chehab <mchehab@s-opensource.com>
275 lines
9.8 KiB
ReStructuredText
275 lines
9.8 KiB
ReStructuredText
.. -*- coding: utf-8; mode: rst -*-
|
|
|
|
.. _VIDIOC_QUERYCAP:
|
|
|
|
*********************
|
|
ioctl VIDIOC_QUERYCAP
|
|
*********************
|
|
|
|
Name
|
|
====
|
|
|
|
VIDIOC_QUERYCAP - Query device capabilities
|
|
|
|
|
|
Synopsis
|
|
========
|
|
|
|
.. c:function:: int ioctl( int fd, VIDIOC_QUERYCAP, struct v4l2_capability *argp )
|
|
:name: VIDIOC_QUERYCAP
|
|
|
|
|
|
Arguments
|
|
=========
|
|
|
|
``fd``
|
|
File descriptor returned by :ref:`open() <func-open>`.
|
|
|
|
``argp``
|
|
Pointer to struct :c:type:`v4l2_capability`.
|
|
|
|
|
|
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 :c:type:`v4l2_capability` which is
|
|
filled by the driver. When the driver is not compatible with this
|
|
specification the ioctl returns an ``EINVAL`` error code.
|
|
|
|
|
|
.. tabularcolumns:: |p{1.5cm}|p{2.5cm}|p{13cm}|
|
|
|
|
.. c:type:: v4l2_capability
|
|
|
|
.. flat-table:: struct v4l2_capability
|
|
:header-rows: 0
|
|
:stub-columns: 0
|
|
:widths: 3 4 20
|
|
|
|
* - __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.
|
|
* - __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.
|
|
* - __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.
|
|
* - __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. For example if the media stack corresponds to the V4L2
|
|
version shipped with Kernel 4.14, it would be equivalent to:
|
|
* - :cspan:`2`
|
|
|
|
``#define KERNEL_VERSION(a,b,c) (((a) << 16) + ((b) << 8) + (c))``
|
|
|
|
``__u32 version = KERNEL_VERSION(4, 14, 0);``
|
|
|
|
``printf ("Version: %u.%u.%u\\n",``
|
|
|
|
``(version >> 16) & 0xFF, (version >> 8) & 0xFF, version & 0xFF);``
|
|
* - __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.
|
|
* - __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``.
|
|
* - __u32
|
|
- ``reserved``\ [3]
|
|
- Reserved for future extensions. Drivers must set this array to
|
|
zero.
|
|
|
|
|
|
|
|
.. tabularcolumns:: |p{6.1cm}|p{2.2cm}|p{8.7cm}|
|
|
|
|
.. _device-capabilities:
|
|
|
|
.. cssclass:: longtable
|
|
|
|
.. flat-table:: Device Capabilities Flags
|
|
:header-rows: 0
|
|
:stub-columns: 0
|
|
:widths: 3 1 4
|
|
|
|
* - ``V4L2_CAP_VIDEO_CAPTURE``
|
|
- 0x00000001
|
|
- The device supports the single-planar API through the
|
|
:ref:`Video Capture <capture>` interface.
|
|
* - ``V4L2_CAP_VIDEO_CAPTURE_MPLANE``
|
|
- 0x00001000
|
|
- The device supports the :ref:`multi-planar API <planar-apis>`
|
|
through the :ref:`Video Capture <capture>` interface.
|
|
* - ``V4L2_CAP_VIDEO_OUTPUT``
|
|
- 0x00000002
|
|
- The device supports the single-planar API through the
|
|
:ref:`Video Output <output>` interface.
|
|
* - ``V4L2_CAP_VIDEO_OUTPUT_MPLANE``
|
|
- 0x00002000
|
|
- The device supports the :ref:`multi-planar API <planar-apis>`
|
|
through the :ref:`Video Output <output>` interface.
|
|
* - ``V4L2_CAP_VIDEO_M2M``
|
|
- 0x00004000
|
|
- The device supports the single-planar API through the Video
|
|
Memory-To-Memory interface.
|
|
* - ``V4L2_CAP_VIDEO_M2M_MPLANE``
|
|
- 0x00008000
|
|
- The device supports the :ref:`multi-planar API <planar-apis>`
|
|
through the Video Memory-To-Memory interface.
|
|
* - ``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.
|
|
* - ``V4L2_CAP_VBI_CAPTURE``
|
|
- 0x00000010
|
|
- The device supports the :ref:`Raw VBI Capture <raw-vbi>`
|
|
interface, providing Teletext and Closed Caption data.
|
|
* - ``V4L2_CAP_VBI_OUTPUT``
|
|
- 0x00000020
|
|
- The device supports the :ref:`Raw VBI Output <raw-vbi>`
|
|
interface.
|
|
* - ``V4L2_CAP_SLICED_VBI_CAPTURE``
|
|
- 0x00000040
|
|
- The device supports the :ref:`Sliced VBI Capture <sliced>`
|
|
interface.
|
|
* - ``V4L2_CAP_SLICED_VBI_OUTPUT``
|
|
- 0x00000080
|
|
- The device supports the :ref:`Sliced VBI Output <sliced>`
|
|
interface.
|
|
* - ``V4L2_CAP_RDS_CAPTURE``
|
|
- 0x00000100
|
|
- The device supports the :ref:`RDS <rds>` capture interface.
|
|
* - ``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]_
|
|
* - ``V4L2_CAP_HW_FREQ_SEEK``
|
|
- 0x00000400
|
|
- The device supports the
|
|
:ref:`VIDIOC_S_HW_FREQ_SEEK` ioctl
|
|
for hardware frequency seeking.
|
|
* - ``V4L2_CAP_RDS_OUTPUT``
|
|
- 0x00000800
|
|
- The device supports the :ref:`RDS <rds>` output interface.
|
|
* - ``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`.
|
|
* - ``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`.
|
|
* - ``V4L2_CAP_RADIO``
|
|
- 0x00040000
|
|
- This is a radio receiver.
|
|
* - ``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`.
|
|
* - ``V4L2_CAP_SDR_CAPTURE``
|
|
- 0x00100000
|
|
- The device supports the :ref:`SDR Capture <sdr>` interface.
|
|
* - ``V4L2_CAP_EXT_PIX_FORMAT``
|
|
- 0x00200000
|
|
- The device supports the struct
|
|
:c:type:`v4l2_pix_format` extended fields.
|
|
* - ``V4L2_CAP_SDR_OUTPUT``
|
|
- 0x00400000
|
|
- The device supports the :ref:`SDR Output <sdr>` interface.
|
|
* - ``V4L2_CAP_META_CAPTURE``
|
|
- 0x00800000
|
|
- The device supports the :ref:`metadata` capture interface.
|
|
* - ``V4L2_CAP_READWRITE``
|
|
- 0x01000000
|
|
- The device supports the :ref:`read() <rw>` and/or
|
|
:ref:`write() <rw>` I/O methods.
|
|
* - ``V4L2_CAP_ASYNCIO``
|
|
- 0x02000000
|
|
- The device supports the :ref:`asynchronous <async>` I/O methods.
|
|
* - ``V4L2_CAP_STREAMING``
|
|
- 0x04000000
|
|
- The device supports the :ref:`streaming <mmap>` I/O method.
|
|
* - ``V4L2_CAP_TOUCH``
|
|
- 0x10000000
|
|
- This is a touch device.
|
|
* - ``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 :c:type:`v4l2_framebuffer` lacks an
|
|
enum :c:type:`v4l2_buf_type` field, therefore the
|
|
type of overlay is implied by the driver capabilities.
|