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diff --git a/Documentation/userspace-api/media/v4l/vidioc-querycap.rst b/Documentation/userspace-api/media/v4l/vidioc-querycap.rst new file mode 100644 index 0000000000..6c57b84283 --- /dev/null +++ b/Documentation/userspace-api/media/v4l/vidioc-querycap.rst @@ -0,0 +1,278 @@ +.. SPDX-License-Identifier: GFDL-1.1-no-invariants-or-later +.. c:namespace:: V4L + +.. _VIDIOC_QUERYCAP: + +********************* +ioctl VIDIOC_QUERYCAP +********************* + +Name +==== + +VIDIOC_QUERYCAP - Query device capabilities + +Synopsis +======== + +.. c:macro:: VIDIOC_QUERYCAP + +``int ioctl(int fd, VIDIOC_QUERYCAP, struct v4l2_capability *argp)`` + +Arguments +========= + +``fd`` + File descriptor returned by :c: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. + +.. c:type:: v4l2_capability + +.. tabularcolumns:: |p{1.4cm}|p{2.8cm}|p{13.1cm}| + +.. cssclass:: longtable + +.. 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:vivid-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{7.0cm}|p{2.6cm}|p{7.7cm}| + +.. _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`` + - 0x00008000 + - The device supports the single-planar API through the Video + Memory-To-Memory interface. + * - ``V4L2_CAP_VIDEO_M2M_MPLANE`` + - 0x00004000 + - 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 :c:func:`read()` and/or + :c:func:`write()` I/O methods. + * - ``V4L2_CAP_STREAMING`` + - 0x04000000 + - The device supports the :ref:`streaming <mmap>` I/O method. + * - ``V4L2_CAP_META_OUTPUT`` + - 0x08000000 + - The device supports the :ref:`metadata` output interface. + * - ``V4L2_CAP_TOUCH`` + - 0x10000000 + - This is a touch device. + * - ``V4L2_CAP_IO_MC`` + - 0x20000000 + - There is only one input and/or output seen from userspace. The whole + video topology configuration, including which I/O entity is routed to + the input/output, is configured by userspace via the Media Controller. + See :ref:`media_controller`. + * - ``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. |