target/linux/bcm27xx/patches-5.15/950-0637-media-v4l2-ctrls-Document-V4L2_CID_NOTIFY_GAINS-cont.patch

   1 From dd91fe58de578570d49fe644eb05398a27510478 Mon Sep 17 00:00:00 2001
   2 From: David Plowman <david.plowman@raspberrypi.com>
   3 Date: Mon, 16 Aug 2021 13:39:09 +0200
   4 Subject: [PATCH] media: v4l2-ctrls: Document V4L2_CID_NOTIFY_GAINS
   5  control
   6
   7 commit 311a839a1ad255ebcb7291fb4e0d2ec2f32312a7 upstream.
   8
   9 Add documentation for the V4L2_CID_NOTIFY_GAINS control.
  10
  11 This control is required by sensors that need to know what colour
  12 gains will be applied to pixels by downstream processing (such as by
  13 an ISP), though the sensor does not apply these gains itself.
  14
  15 Signed-off-by: David Plowman <david.plowman@raspberrypi.com>
  16 Reviewed-by: Laurent Pinchart <laurent.pinchart@ideasonboard.com>
  17 Signed-off-by: Sakari Ailus <sakari.ailus@linux.intel.com>
  18 Signed-off-by: Mauro Carvalho Chehab <mchehab+huawei@kernel.org>
  19 ---
  20  .../media/v4l/ext-ctrls-image-source.rst      | 20 +++++++++++++++++++
  21  1 file changed, 20 insertions(+)
  22
  23 --- a/Documentation/userspace-api/media/v4l/ext-ctrls-image-source.rst
  24 +++ b/Documentation/userspace-api/media/v4l/ext-ctrls-image-source.rst
  25 @@ -72,3 +72,23 @@ Image Source Control IDs
  26      * - __u32
  27        - ``height``
  28        - Height of the area.
  29 +
  30 +``V4L2_CID_NOTIFY_GAINS (integer array)``
  31 +    The sensor is notified what gains will be applied to the different
  32 +    colour channels by subsequent processing (such as by an ISP). The
  33 +    sensor is merely informed of these values in case it performs
  34 +    processing that requires them, but it does not apply them itself to
  35 +    the output pixels.
  36 +
  37 +    Currently it is defined only for Bayer sensors, and is an array
  38 +    control taking 4 gain values, being the gains for each of the
  39 +    Bayer channels. The gains are always in the order B, Gb, Gr and R,
  40 +    irrespective of the exact Bayer order of the sensor itself.
  41 +
  42 +    The use of an array allows this control to be extended to sensors
  43 +    with, for example, non-Bayer CFAs (colour filter arrays).
  44 +
  45 +    The units for the gain values are linear, with the default value
  46 +    representing a gain of exactly 1.0. For example, if this default value
  47 +    is reported as being (say) 128, then a value of 192 would represent
  48 +    a gain of exactly 1.5.