1.. -*- coding: utf-8; mode: rst -*- 2 3.. _VIDIOC_SUBDEV_G_FRAME_INTERVAL: 4 5******************************************************************** 6ioctl VIDIOC_SUBDEV_G_FRAME_INTERVAL, VIDIOC_SUBDEV_S_FRAME_INTERVAL 7******************************************************************** 8 9Name 10==== 11 12VIDIOC_SUBDEV_G_FRAME_INTERVAL - VIDIOC_SUBDEV_S_FRAME_INTERVAL - Get or set the frame interval on a subdev pad 13 14 15Synopsis 16======== 17 18.. c:function:: int ioctl( int fd, VIDIOC_SUBDEV_G_FRAME_INTERVAL, struct v4l2_subdev_frame_interval *argp ) 19 :name: VIDIOC_SUBDEV_G_FRAME_INTERVAL 20 21.. c:function:: int ioctl( int fd, VIDIOC_SUBDEV_S_FRAME_INTERVAL, struct v4l2_subdev_frame_interval *argp ) 22 :name: VIDIOC_SUBDEV_S_FRAME_INTERVAL 23 24 25Arguments 26========= 27 28``fd`` 29 File descriptor returned by :ref:`open() <func-open>`. 30 31``argp`` 32 Pointer to struct :c:type:`v4l2_subdev_frame_interval`. 33 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 61Drivers must not return an error solely because the requested interval 62doesn't match the device capabilities. They must instead modify the 63interval to match what the hardware can provide. The modified interval 64should be as close as possible to the original request. 65 66Sub-devices that support the frame interval ioctls should implement them 67on a single pad only. Their behaviour when supported on multiple pads of 68the same sub-device is not defined. 69 70 71.. c:type:: v4l2_subdev_frame_interval 72 73.. tabularcolumns:: |p{4.4cm}|p{4.4cm}|p{8.7cm}| 74 75.. flat-table:: struct v4l2_subdev_frame_interval 76 :header-rows: 0 77 :stub-columns: 0 78 :widths: 1 1 2 79 80 * - __u32 81 - ``pad`` 82 - Pad number as reported by the media controller API. 83 * - struct :c:type:`v4l2_fract` 84 - ``interval`` 85 - Period, in seconds, between consecutive video frames. 86 * - __u32 87 - ``reserved``\ [9] 88 - Reserved for future extensions. Applications and drivers must set 89 the array to zero. 90 91 92Return Value 93============ 94 95On success 0 is returned, on error -1 and the ``errno`` variable is set 96appropriately. The generic error codes are described at the 97:ref:`Generic Error Codes <gen-errors>` chapter. 98 99EBUSY 100 The frame interval can't be changed because the pad is currently 101 busy. This can be caused, for instance, by an active video stream on 102 the pad. The ioctl must not be retried without performing another 103 action to fix the problem first. Only returned by 104 ``VIDIOC_SUBDEV_S_FRAME_INTERVAL`` 105 106EINVAL 107 The struct 108 :c:type:`v4l2_subdev_frame_interval` 109 ``pad`` references a non-existing pad, or the pad doesn't support 110 frame intervals. 111