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diff --git a/Documentation/userspace-api/media/v4l/vidioc-subdev-enum-frame-interval.rst b/Documentation/userspace-api/media/v4l/vidioc-subdev-enum-frame-interval.rst new file mode 100644 index 0000000000..8def4c05d3 --- /dev/null +++ b/Documentation/userspace-api/media/v4l/vidioc-subdev-enum-frame-interval.rst @@ -0,0 +1,114 @@ +.. SPDX-License-Identifier: GFDL-1.1-no-invariants-or-later +.. c:namespace:: V4L + +.. _VIDIOC_SUBDEV_ENUM_FRAME_INTERVAL: + +*************************************** +ioctl VIDIOC_SUBDEV_ENUM_FRAME_INTERVAL +*************************************** + +Name +==== + +VIDIOC_SUBDEV_ENUM_FRAME_INTERVAL - Enumerate frame intervals + +Synopsis +======== + +.. c:macro:: VIDIOC_SUBDEV_ENUM_FRAME_INTERVAL + +``int ioctl(int fd, VIDIOC_SUBDEV_ENUM_FRAME_INTERVAL, struct v4l2_subdev_frame_interval_enum * argp)`` + +Arguments +========= + +``fd`` + File descriptor returned by :c:func:`open()`. + +``argp`` + Pointer to struct :c:type:`v4l2_subdev_frame_interval_enum`. + +Description +=========== + +This ioctl lets applications enumerate available frame intervals on a +given sub-device pad. Frame intervals only makes sense for sub-devices +that can control the frame period on their own. This includes, for +instance, image sensors and TV tuners. + +For the common use case of image sensors, the frame intervals available +on the sub-device output pad depend on the frame format and size on the +same pad. Applications must thus specify the desired format and size +when enumerating frame intervals. + +To enumerate frame intervals applications initialize the ``index``, +``pad``, ``which``, ``code``, ``width`` and ``height`` fields of struct +:c:type:`v4l2_subdev_frame_interval_enum` +and call the :ref:`VIDIOC_SUBDEV_ENUM_FRAME_INTERVAL` ioctl with a pointer +to this structure. Drivers fill the rest of the structure or return an +EINVAL error code if one of the input fields is invalid. All frame +intervals are enumerable by beginning at index zero and incrementing by +one until ``EINVAL`` is returned. + +Available frame intervals may depend on the current 'try' formats at +other pads of the sub-device, as well as on the current active links. +See :ref:`VIDIOC_SUBDEV_G_FMT` for more +information about the try formats. + +Sub-devices that support the frame interval enumeration ioctl should +implemented it on a single pad only. Its behaviour when supported on +multiple pads of the same sub-device is not defined. + +.. c:type:: v4l2_subdev_frame_interval_enum + +.. tabularcolumns:: |p{4.4cm}|p{4.4cm}|p{8.5cm}| + +.. flat-table:: struct v4l2_subdev_frame_interval_enum + :header-rows: 0 + :stub-columns: 0 + :widths: 1 1 2 + + * - __u32 + - ``index`` + - Number of the format in the enumeration, set by the application. + * - __u32 + - ``pad`` + - Pad number as reported by the media controller API. + * - __u32 + - ``code`` + - The media bus format code, as defined in + :ref:`v4l2-mbus-format`. + * - __u32 + - ``width`` + - Frame width, in pixels. + * - __u32 + - ``height`` + - Frame height, in pixels. + * - struct :c:type:`v4l2_fract` + - ``interval`` + - Period, in seconds, between consecutive video frames. + * - __u32 + - ``which`` + - Frame intervals to be enumerated, from enum + :ref:`v4l2_subdev_format_whence <v4l2-subdev-format-whence>`. + * - __u32 + - ``stream`` + - Stream identifier. + * - __u32 + - ``reserved``\ [7] + - Reserved for future extensions. Applications and drivers must set + the array to zero. + +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. + +EINVAL + The struct + :c:type:`v4l2_subdev_frame_interval_enum` + ``pad`` references a non-existing pad, one of the ``code``, + ``width`` or ``height`` fields are invalid for the given pad or the + ``index`` field is out of bounds. |