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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: Sakari Ailus <sakari.ailus@linux.intel.com>
Signed-off-by: Mauro Carvalho Chehab <mchehab+huawei@kernel.org>

authored by

Sakari Ailus and committed by
Mauro Carvalho Chehab e5a466d4 8925b530

+10 -13
+10 -13
Documentation/userspace-api/media/v4l/ext-ctrls-image-process.rst
··· 23 23 .. _v4l2-cid-link-freq: 24 24 25 25 ``V4L2_CID_LINK_FREQ (integer menu)`` 26 - Data bus frequency. Together with the media bus pixel code, bus type 27 - (clock cycles per sample), the data bus frequency defines the pixel 28 - rate (``V4L2_CID_PIXEL_RATE``) in the pixel array (or possibly 29 - elsewhere, if the device is not an image sensor). The frame rate can 30 - be calculated from the pixel clock, image width and height and 31 - horizontal and vertical blanking. While the pixel rate control may 32 - be defined elsewhere than in the subdev containing the pixel array, 33 - the frame rate cannot be obtained from that information. This is 34 - because only on the pixel array it can be assumed that the vertical 35 - and horizontal blanking information is exact: no other blanking is 36 - allowed in the pixel array. The selection of frame rate is performed 37 - by selecting the desired horizontal and vertical blanking. The unit 38 - of this control is Hz. 26 + The frequency of the data bus (e.g. parallel or CSI-2). 39 27 40 28 .. _v4l2-cid-pixel-rate: 41 29 42 30 ``V4L2_CID_PIXEL_RATE (64-bit integer)`` 43 31 Pixel sampling rate in the device's pixel array. This control is 44 32 read-only and its unit is pixels / second. 33 + 34 + Some devices use horizontal and vertical balanking to configure the frame 35 + rate. The frame rate can be calculated from the pixel rate, analogue crop 36 + rectangle as well as horizontal and vertical blanking. The pixel rate 37 + control may be present in a different sub-device than the blanking controls 38 + and the analogue crop rectangle configuration. 39 + 40 + The configuration of the frame rate is performed by selecting the desired 41 + horizontal and vertical blanking. The unit of this control is Hz. 45 42 46 43 ``V4L2_CID_TEST_PATTERN (menu)`` 47 44 Some capture/display/sensor devices have the capability to generate