From 849369d6c66d3054688672f97d31fceb8e8230fb Mon Sep 17 00:00:00 2001 From: root Date: Fri, 25 Dec 2015 04:40:36 +0000 Subject: initial_commit --- Documentation/DocBook/v4l/vidioc-subdev-g-fmt.xml | 180 ++++++++++++++++++++++ 1 file changed, 180 insertions(+) create mode 100644 Documentation/DocBook/v4l/vidioc-subdev-g-fmt.xml (limited to 'Documentation/DocBook/v4l/vidioc-subdev-g-fmt.xml') diff --git a/Documentation/DocBook/v4l/vidioc-subdev-g-fmt.xml b/Documentation/DocBook/v4l/vidioc-subdev-g-fmt.xml new file mode 100644 index 00000000..f367c570 --- /dev/null +++ b/Documentation/DocBook/v4l/vidioc-subdev-g-fmt.xml @@ -0,0 +1,180 @@ + + + ioctl VIDIOC_SUBDEV_G_FMT, VIDIOC_SUBDEV_S_FMT + &manvol; + + + + VIDIOC_SUBDEV_G_FMT + VIDIOC_SUBDEV_S_FMT + Get or set the data format on a subdev pad + + + + + + int ioctl + int fd + int request + struct v4l2_subdev_format *argp + + + + + + + Arguments + + + + fd + + &fd; + + + + request + + VIDIOC_SUBDEV_G_FMT, VIDIOC_SUBDEV_S_FMT + + + + argp + + + + + + + + + Description + + + Experimental + This is an experimental + interface and may change in the future. + + + These ioctls are used to negotiate the frame format at specific + subdev pads in the image pipeline. + + To retrieve the current format applications set the + pad field of a &v4l2-subdev-format; to the + desired pad number as reported by the media API and the + which field to + V4L2_SUBDEV_FORMAT_ACTIVE. When they call the + VIDIOC_SUBDEV_G_FMT ioctl with a pointer to this + structure the driver fills the members of the format + field. + + To change the current format applications set both the + pad and which fields + and all members of the format field. When they + call the VIDIOC_SUBDEV_S_FMT ioctl with a pointer to this + structure the driver verifies the requested format, adjusts it based on the + hardware capabilities and configures the device. Upon return the + &v4l2-subdev-format; contains the current format as would be returned by a + VIDIOC_SUBDEV_G_FMT call. + + Applications can query the device capabilities by setting the + which to + V4L2_SUBDEV_FORMAT_TRY. When set, 'try' formats are not + applied to the device by the driver, but are changed exactly as active + formats and stored in the sub-device file handle. Two applications querying + the same sub-device would thus not interact with each other. + + For instance, to try a format at the output pad of a sub-device, + applications would first set the try format at the sub-device input with the + VIDIOC_SUBDEV_S_FMT ioctl. They would then either + retrieve the default format at the output pad with the + VIDIOC_SUBDEV_G_FMT ioctl, or set the desired output + pad format with the VIDIOC_SUBDEV_S_FMT ioctl and check + the returned value. + + Try formats do not depend on active formats, but can depend on the + current links configuration or sub-device controls value. For instance, a + low-pass noise filter might crop pixels at the frame boundaries, modifying + its output frame size. + + Drivers must not return an error solely because the requested format + doesn't match the device capabilities. They must instead modify the format + to match what the hardware can provide. The modified format should be as + close as possible to the original request. + + + struct <structname>v4l2_subdev_format</structname> + + &cs-str; + + + __u32 + pad + Pad number as reported by the media controller API. + + + __u32 + which + Format to modified, from &v4l2-subdev-format-whence;. + + + &v4l2-mbus-framefmt; + format + Definition of an image format, see for details. + + + __u32 + reserved[8] + Reserved for future extensions. Applications and drivers must + set the array to zero. + + + +
+ + + enum <structname>v4l2_subdev_format_whence</structname> + + &cs-def; + + + V4L2_SUBDEV_FORMAT_TRY + 0 + Try formats, used for querying device capabilities. + + + V4L2_SUBDEV_FORMAT_ACTIVE + 1 + Active formats, applied to the hardware. + + + +
+ + + + &return-value; + + + + EBUSY + + The format 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_FMT + + + + EINVAL + + The &v4l2-subdev-format; pad + references a non-existing pad, or the which + field references a non-existing format. + + + + + -- cgit v1.2.3