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+.. -*- coding: utf-8; mode: rst -*-
+
+.. _VIDIOC_SUBDEV_G_FRAME_INTERVAL:
+
+********************************************************************
+ioctl VIDIOC_SUBDEV_G_FRAME_INTERVAL, VIDIOC_SUBDEV_S_FRAME_INTERVAL
+********************************************************************
+
+Name
+====
+
+VIDIOC_SUBDEV_G_FRAME_INTERVAL - VIDIOC_SUBDEV_S_FRAME_INTERVAL - Get or set the frame interval on a subdev pad
+
+
+Synopsis
+========
+
+.. cpp:function:: int ioctl( int fd, int request, struct v4l2_subdev_frame_interval *argp )
+
+
+Arguments
+=========
+
+``fd``
+    File descriptor returned by :ref:`open() <func-open>`.
+
+``request``
+    VIDIOC_SUBDEV_G_FRAME_INTERVAL,
+    VIDIOC_SUBDEV_S_FRAME_INTERVAL
+
+``argp``
+
+
+Description
+===========
+
+These ioctls are used to get and set the frame interval at specific
+subdev pads in the image pipeline. The frame interval only makes sense
+for sub-devices that can control the frame period on their own. This
+includes, for instance, image sensors and TV tuners. Sub-devices that
+don't support frame intervals must not implement these ioctls.
+
+To retrieve the current frame interval applications set the ``pad``
+field of a struct
+:ref:`v4l2_subdev_frame_interval <v4l2-subdev-frame-interval>` to
+the desired pad number as reported by the media controller API. When
+they call the ``VIDIOC_SUBDEV_G_FRAME_INTERVAL`` ioctl with a pointer to
+this structure the driver fills the members of the ``interval`` field.
+
+To change the current frame interval applications set both the ``pad``
+field and all members of the ``interval`` field. When they call the
+``VIDIOC_SUBDEV_S_FRAME_INTERVAL`` ioctl with a pointer to this
+structure the driver verifies the requested interval, adjusts it based
+on the hardware capabilities and configures the device. Upon return the
+struct
+:ref:`v4l2_subdev_frame_interval <v4l2-subdev-frame-interval>`
+contains the current frame interval as would be returned by a
+``VIDIOC_SUBDEV_G_FRAME_INTERVAL`` call.
+
+Drivers must not return an error solely because the requested interval
+doesn't match the device capabilities. They must instead modify the
+interval to match what the hardware can provide. The modified interval
+should be as close as possible to the original request.
+
+Sub-devices that support the frame interval ioctls should implement them
+on a single pad only. Their behaviour when supported on multiple pads of
+the same sub-device is not defined.
+
+
+.. _v4l2-subdev-frame-interval:
+
+.. flat-table:: struct v4l2_subdev_frame_interval
+    :header-rows:  0
+    :stub-columns: 0
+    :widths:       1 1 2
+
+
+    -  .. row 1
+
+       -  __u32
+
+       -  ``pad``
+
+       -  Pad number as reported by the media controller API.
+
+    -  .. row 2
+
+       -  struct :ref:`v4l2_fract <v4l2-fract>`
+
+       -  ``interval``
+
+       -  Period, in seconds, between consecutive video frames.
+
+    -  .. row 3
+
+       -  __u32
+
+       -  ``reserved``\ [9]
+
+       -  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.
+
+EBUSY
+    The frame interval can't be changed because the pad is currently
+    busy. This can be caused, for instance, by an active video stream on
+    the pad. The ioctl must not be retried without performing another
+    action to fix the problem first. Only returned by
+    ``VIDIOC_SUBDEV_S_FRAME_INTERVAL``
+
+EINVAL
+    The struct
+    :ref:`v4l2_subdev_frame_interval <v4l2-subdev-frame-interval>`
+    ``pad`` references a non-existing pad, or the pad doesn't support
+    frame intervals.