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diff --git a/Documentation/userspace-api/media/v4l/vidioc-subdev-enum-frame-size.rst b/Documentation/userspace-api/media/v4l/vidioc-subdev-enum-frame-size.rst new file mode 100644 index 0000000000..e3ae84df54 --- /dev/null +++ b/Documentation/userspace-api/media/v4l/vidioc-subdev-enum-frame-size.rst @@ -0,0 +1,132 @@ +.. SPDX-License-Identifier: GFDL-1.1-no-invariants-or-later +.. c:namespace:: V4L + +.. _VIDIOC_SUBDEV_ENUM_FRAME_SIZE: + +*********************************** +ioctl VIDIOC_SUBDEV_ENUM_FRAME_SIZE +*********************************** + +Name +==== + +VIDIOC_SUBDEV_ENUM_FRAME_SIZE - Enumerate media bus frame sizes + +Synopsis +======== + +.. c:macro:: VIDIOC_SUBDEV_ENUM_FRAME_SIZE + +``int ioctl(int fd, VIDIOC_SUBDEV_ENUM_FRAME_SIZE, struct v4l2_subdev_frame_size_enum * argp)`` + +Arguments +========= + +``fd`` + File descriptor returned by :c:func:`open()`. + +``argp`` + Pointer to struct :c:type:`v4l2_subdev_frame_size_enum`. + +Description +=========== + +This ioctl allows applications to access the enumeration of frame sizes +supported by a sub-device on the specified pad +for the specified media bus format. +Supported formats can be retrieved with the +:ref:`VIDIOC_SUBDEV_ENUM_MBUS_CODE` +ioctl. + +The enumerations are defined by the driver, and indexed using the ``index`` field +of the struct :c:type:`v4l2_subdev_frame_size_enum`. +Each pair of ``pad`` and ``code`` correspond to a separate enumeration. +Each enumeration starts with the ``index`` of 0, and +the lowest invalid index marks the end of the enumeration. + +Therefore, to enumerate frame sizes allowed on the specified pad +and using the specified mbus format, initialize the +``pad``, ``which``, and ``code`` fields to desired values, +and set ``index`` to 0. +Then call the :ref:`VIDIOC_SUBDEV_ENUM_FRAME_SIZE` ioctl with a pointer to the +structure. + +A successful call will return with minimum and maximum frame sizes filled in. +Repeat with increasing ``index`` until ``EINVAL`` is received. +``EINVAL`` means that either no more entries are available in the enumeration, +or that an input parameter was invalid. + +Sub-devices that only support discrete frame sizes (such as most +sensors) will return one or more frame sizes with identical minimum and +maximum values. + +Not all possible sizes in given [minimum, maximum] ranges need to be +supported. For instance, a scaler that uses a fixed-point scaling ratio +might not be able to produce every frame size between the minimum and +maximum values. Applications must use the +:ref:`VIDIOC_SUBDEV_S_FMT <VIDIOC_SUBDEV_G_FMT>` ioctl to try the +sub-device for an exact supported frame size. + +Available frame sizes may depend on the current 'try' formats at other +pads of the sub-device, as well as on the current active links and the +current values of V4L2 controls. See +:ref:`VIDIOC_SUBDEV_G_FMT` for more +information about try formats. + +.. c:type:: v4l2_subdev_frame_size_enum + +.. tabularcolumns:: |p{4.4cm}|p{4.4cm}|p{8.5cm}| + +.. flat-table:: struct v4l2_subdev_frame_size_enum + :header-rows: 0 + :stub-columns: 0 + :widths: 1 1 2 + + * - __u32 + - ``index`` + - Index of the frame size in the enumeration belonging to the given pad + and format. Filled in by the application. + * - __u32 + - ``pad`` + - Pad number as reported by the media controller API. + Filled in by the application. + * - __u32 + - ``code`` + - The media bus format code, as defined in + :ref:`v4l2-mbus-format`. Filled in by the application. + * - __u32 + - ``min_width`` + - Minimum frame width, in pixels. Filled in by the driver. + * - __u32 + - ``max_width`` + - Maximum frame width, in pixels. Filled in by the driver. + * - __u32 + - ``min_height`` + - Minimum frame height, in pixels. Filled in by the driver. + * - __u32 + - ``max_height`` + - Maximum frame height, in pixels. Filled in by the driver. + * - __u32 + - ``which`` + - Frame sizes 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_size_enum` + ``pad`` references a non-existing pad, the ``code`` is invalid for + the given pad or the ``index`` field is out of bounds. |