1.. Permission is granted to copy, distribute and/or modify this 2.. document under the terms of the GNU Free Documentation License, 3.. Version 1.1 or any later version published by the Free Software 4.. Foundation, with no Invariant Sections, no Front-Cover Texts 5.. and no Back-Cover Texts. A copy of the license is included at 6.. Documentation/media/uapi/fdl-appendix.rst. 7.. 8.. TODO: replace it to GFDL-1.1-or-later WITH no-invariant-sections 9 10.. _VIDIOC_SUBDEV_G_FRAME_INTERVAL: 11 12******************************************************************** 13ioctl VIDIOC_SUBDEV_G_FRAME_INTERVAL, VIDIOC_SUBDEV_S_FRAME_INTERVAL 14******************************************************************** 15 16Name 17==== 18 19VIDIOC_SUBDEV_G_FRAME_INTERVAL - VIDIOC_SUBDEV_S_FRAME_INTERVAL - Get or set the frame interval on a subdev pad 20 21 22Synopsis 23======== 24 25.. c:function:: int ioctl( int fd, VIDIOC_SUBDEV_G_FRAME_INTERVAL, struct v4l2_subdev_frame_interval *argp ) 26 :name: VIDIOC_SUBDEV_G_FRAME_INTERVAL 27 28.. c:function:: int ioctl( int fd, VIDIOC_SUBDEV_S_FRAME_INTERVAL, struct v4l2_subdev_frame_interval *argp ) 29 :name: VIDIOC_SUBDEV_S_FRAME_INTERVAL 30 31 32Arguments 33========= 34 35``fd`` 36 File descriptor returned by :ref:`open() <func-open>`. 37 38``argp`` 39 Pointer to struct :c:type:`v4l2_subdev_frame_interval`. 40 41 42Description 43=========== 44 45These ioctls are used to get and set the frame interval at specific 46subdev pads in the image pipeline. The frame interval only makes sense 47for sub-devices that can control the frame period on their own. This 48includes, for instance, image sensors and TV tuners. Sub-devices that 49don't support frame intervals must not implement these ioctls. 50 51To retrieve the current frame interval applications set the ``pad`` 52field of a struct 53:c:type:`v4l2_subdev_frame_interval` to 54the desired pad number as reported by the media controller API. When 55they call the ``VIDIOC_SUBDEV_G_FRAME_INTERVAL`` ioctl with a pointer to 56this structure the driver fills the members of the ``interval`` field. 57 58To change the current frame interval applications set both the ``pad`` 59field and all members of the ``interval`` field. When they call the 60``VIDIOC_SUBDEV_S_FRAME_INTERVAL`` ioctl with a pointer to this 61structure the driver verifies the requested interval, adjusts it based 62on the hardware capabilities and configures the device. Upon return the 63struct 64:c:type:`v4l2_subdev_frame_interval` 65contains the current frame interval as would be returned by a 66``VIDIOC_SUBDEV_G_FRAME_INTERVAL`` call. 67 68Drivers must not return an error solely because the requested interval 69doesn't match the device capabilities. They must instead modify the 70interval to match what the hardware can provide. The modified interval 71should be as close as possible to the original request. 72 73Changing the frame interval shall never change the format. Changing the 74format, on the other hand, may change the frame interval. 75 76Sub-devices that support the frame interval ioctls should implement them 77on a single pad only. Their behaviour when supported on multiple pads of 78the same sub-device is not defined. 79 80 81.. c:type:: v4l2_subdev_frame_interval 82 83.. tabularcolumns:: |p{4.4cm}|p{4.4cm}|p{8.7cm}| 84 85.. flat-table:: struct v4l2_subdev_frame_interval 86 :header-rows: 0 87 :stub-columns: 0 88 :widths: 1 1 2 89 90 * - __u32 91 - ``pad`` 92 - Pad number as reported by the media controller API. 93 * - struct :c:type:`v4l2_fract` 94 - ``interval`` 95 - Period, in seconds, between consecutive video frames. 96 * - __u32 97 - ``reserved``\ [9] 98 - Reserved for future extensions. Applications and drivers must set 99 the array to zero. 100 101 102Return Value 103============ 104 105On success 0 is returned, on error -1 and the ``errno`` variable is set 106appropriately. The generic error codes are described at the 107:ref:`Generic Error Codes <gen-errors>` chapter. 108 109EBUSY 110 The frame interval can't be changed because the pad is currently 111 busy. This can be caused, for instance, by an active video stream on 112 the pad. The ioctl must not be retried without performing another 113 action to fix the problem first. Only returned by 114 ``VIDIOC_SUBDEV_S_FRAME_INTERVAL`` 115 116EINVAL 117 The struct 118 :c:type:`v4l2_subdev_frame_interval` 119 ``pad`` references a non-existing pad, or the pad doesn't support 120 frame intervals. 121