1.. SPDX-License-Identifier: GFDL-1.1-no-invariants-or-later 2.. c:namespace:: V4L 3 4.. _VIDIOC_SUBDEV_G_FRAME_INTERVAL: 5 6******************************************************************** 7ioctl VIDIOC_SUBDEV_G_FRAME_INTERVAL, VIDIOC_SUBDEV_S_FRAME_INTERVAL 8******************************************************************** 9 10Name 11==== 12 13VIDIOC_SUBDEV_G_FRAME_INTERVAL - VIDIOC_SUBDEV_S_FRAME_INTERVAL - Get or set the frame interval on a subdev pad 14 15Synopsis 16======== 17 18.. c:macro:: VIDIOC_SUBDEV_G_FRAME_INTERVAL 19 20``int ioctl(int fd, VIDIOC_SUBDEV_G_FRAME_INTERVAL, struct v4l2_subdev_frame_interval *argp)`` 21 22.. c:macro:: VIDIOC_SUBDEV_S_FRAME_INTERVAL 23 24``int ioctl(int fd, VIDIOC_SUBDEV_S_FRAME_INTERVAL, struct v4l2_subdev_frame_interval *argp)`` 25 26Arguments 27========= 28 29``fd`` 30 File descriptor returned by :c:func:`open()`. 31 32``argp`` 33 Pointer to struct :c:type:`v4l2_subdev_frame_interval`. 34 35Description 36=========== 37 38These ioctls are used to get and set the frame interval at specific 39subdev pads in the image pipeline. The frame interval only makes sense 40for sub-devices that can control the frame period on their own. This 41includes, for instance, image sensors and TV tuners. Sub-devices that 42don't support frame intervals must not implement these ioctls. 43 44To retrieve the current frame interval applications set the ``pad`` 45field of a struct 46:c:type:`v4l2_subdev_frame_interval` to 47the desired pad number as reported by the media controller API. When 48they call the ``VIDIOC_SUBDEV_G_FRAME_INTERVAL`` ioctl with a pointer to 49this structure the driver fills the members of the ``interval`` field. 50 51To change the current frame interval applications set both the ``pad`` 52field and all members of the ``interval`` field. When they call the 53``VIDIOC_SUBDEV_S_FRAME_INTERVAL`` ioctl with a pointer to this 54structure the driver verifies the requested interval, adjusts it based 55on the hardware capabilities and configures the device. Upon return the 56struct 57:c:type:`v4l2_subdev_frame_interval` 58contains the current frame interval as would be returned by a 59``VIDIOC_SUBDEV_G_FRAME_INTERVAL`` call. 60 61If the subdev device node has been registered in read-only mode, calls to 62``VIDIOC_SUBDEV_S_FRAME_INTERVAL`` are only valid if the ``which`` field is set 63to ``V4L2_SUBDEV_FORMAT_TRY``, otherwise an error is returned and the errno 64variable is set to ``-EPERM``. 65 66Drivers must not return an error solely because the requested interval 67doesn't match the device capabilities. They must instead modify the 68interval to match what the hardware can provide. The modified interval 69should be as close as possible to the original request. 70 71Changing the frame interval shall never change the format. Changing the 72format, on the other hand, may change the frame interval. 73 74Sub-devices that support the frame interval ioctls should implement them 75on a single pad only. Their behaviour when supported on multiple pads of 76the same sub-device is not defined. 77 78.. c:type:: v4l2_subdev_frame_interval 79 80.. tabularcolumns:: |p{4.4cm}|p{4.4cm}|p{8.5cm}| 81 82.. flat-table:: struct v4l2_subdev_frame_interval 83 :header-rows: 0 84 :stub-columns: 0 85 :widths: 1 1 2 86 87 * - __u32 88 - ``pad`` 89 - Pad number as reported by the media controller API. 90 * - struct :c:type:`v4l2_fract` 91 - ``interval`` 92 - Period, in seconds, between consecutive video frames. 93 * - __u32 94 - ``stream`` 95 - Stream identifier. 96 * - __u32 97 - ``which`` 98 - Active or try frame interval, from enum 99 :ref:`v4l2_subdev_format_whence <v4l2-subdev-format-whence>`. 100 * - __u32 101 - ``reserved``\ [7] 102 - Reserved for future extensions. Applications and drivers must set 103 the array to zero. 104 105Return Value 106============ 107 108On success 0 is returned, on error -1 and the ``errno`` variable is set 109appropriately. The generic error codes are described at the 110:ref:`Generic Error Codes <gen-errors>` chapter. 111 112EBUSY 113 The frame interval can't be changed because the pad is currently 114 busy. This can be caused, for instance, by an active video stream on 115 the pad. The ioctl must not be retried without performing another 116 action to fix the problem first. Only returned by 117 ``VIDIOC_SUBDEV_S_FRAME_INTERVAL`` 118 119EINVAL 120 The struct :c:type:`v4l2_subdev_frame_interval` ``pad`` references a 121 non-existing pad, the ``which`` field has an unsupported value, or the pad 122 doesn't support frame intervals. 123 124EPERM 125 The ``VIDIOC_SUBDEV_S_FRAME_INTERVAL`` ioctl has been called on a read-only 126 subdevice and the ``which`` field is set to ``V4L2_SUBDEV_FORMAT_ACTIVE``. 127