media: v4l: uapi: ccs: Add controls for CCS alternative analogue gain

Add two new controls for alternative analogue gain some CCS compliant
camera sensors support.

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

1 files changed, 13 insertions, 0 deletions

diff --git a/Documentation/userspace-api/media/drivers/ccs.rst b/Documentation/userspace-api/media/drivers/ccs.rst
index a95d7941533d..ea09c8139c23 100644
--- a/Documentation/userspace-api/media/drivers/ccs.rst
+++ b/Documentation/userspace-api/media/drivers/ccs.rst
@@ -81,4 +81,17 @@ obtained from the following controls:
 The analogue gain (``x`` in the formula) is controlled through
 ``V4L2_CID_ANALOGUE_GAIN`` in this case.
 
+Alternate analogue gain model
+~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
+
+The CCS defines another analogue gain model called alternate analogue gain. In
+this case, the formula to calculate actual gain consists of linear and
+exponential parts:
+
+	gain = linear * 2 ^ exponent
+
+The ``linear`` and ``exponent`` factors can be set using the
+``V4L2_CID_CCS_ANALOGUE_LINEAR_GAIN`` and
+``V4L2_CID_CCS_ANALOGUE_EXPONENTIAL_GAIN`` controls, respectively
+
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