Commit e5a466d4 authored by Sakari Ailus's avatar Sakari Ailus Committed by Mauro Carvalho Chehab
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media: Documentation: v4l: Improve frame rate configuration documentation 



Improve the documentation of the frame rate configuration so that it can
be understood by a regular human being.

Signed-off-by: default avatarSakari Ailus <sakari.ailus@linux.intel.com>
Signed-off-by: default avatarMauro Carvalho Chehab <mchehab+huawei@kernel.org>
parent 8925b530

Documentation/userspace-api/media/v4l/ext-ctrls-image-process.rst

+10 −13
Original line number Diff line number Diff line
@@ -23,19 +23,7 @@ Image Process Control IDs 
.. _v4l2-cid-link-freq:



``V4L2_CID_LINK_FREQ (integer menu)``

    Data bus frequency. Together with the media bus pixel code, bus type

    (clock cycles per sample), the data bus frequency defines the pixel

    rate (``V4L2_CID_PIXEL_RATE``) in the pixel array (or possibly

    elsewhere, if the device is not an image sensor). The frame rate can

    be calculated from the pixel clock, image width and height and

    horizontal and vertical blanking. While the pixel rate control may

    be defined elsewhere than in the subdev containing the pixel array,

    the frame rate cannot be obtained from that information. This is

    because only on the pixel array it can be assumed that the vertical

    and horizontal blanking information is exact: no other blanking is

    allowed in the pixel array. The selection of frame rate is performed

    by selecting the desired horizontal and vertical blanking. The unit

    of this control is Hz.

    The frequency of the data bus (e.g. parallel or CSI-2).



.. _v4l2-cid-pixel-rate:
@@ -43,6 +31,15 @@ Image Process Control IDs 
    Pixel sampling rate in the device's pixel array. This control is

    read-only and its unit is pixels / second.



    Some devices use horizontal and vertical balanking to configure the frame

    rate. The frame rate can be calculated from the pixel rate, analogue crop

    rectangle as well as horizontal and vertical blanking. The pixel rate

    control may be present in a different sub-device than the blanking controls

    and the analogue crop rectangle configuration.



    The configuration of the frame rate is performed by selecting the desired

    horizontal and vertical blanking. The unit of this control is Hz.



``V4L2_CID_TEST_PATTERN (menu)``

    Some capture/display/sensor devices have the capability to generate

    test pattern images. These hardware specific test patterns can be