media: v4l: uapi: ccs: Add CCS controls for shading correction

Add V4L2 controls for controlling CCS lens shading correction as well as
conveying its capabilities.
Signed-off-by: Sakari Ailus <sakari.ailus@linux.intel.com>
Signed-off-by: Mauro Carvalho Chehab <mchehab+huawei@kernel.org>

Documentation/userspace-api/media/drivers/ccs.rst

@@ -94,4 +94,17 @@ 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
 
+Shading correction
+~~~~~~~~~~~~~~~~~~
+
+The CCS standard supports lens shading correction. The feature can be controlled
+using ``V4L2_CID_CCS_SHADING_CORRECTION``. Additionally, the luminance
+correction level may be changed using
+``V4L2_CID_CCS_LUMINANCE_CORRECTION_LEVEL``, where value 0 indicates no
+correction and 128 indicates correcting the luminance in corners to 10 % less
+than in the centre.
+
+Shading correction needs to be enabled for luminance correction level to have an
+effect.
+
 **Copyright** |copy| 2020 Intel Corporation

include/uapi/linux/ccs.h

@@ -12,5 +12,7 @@
 #define V4L2_CID_CCS_ANALOGUE_GAIN_C1		(V4L2_CID_USER_CCS_BASE + 4)
 #define V4L2_CID_CCS_ANALOGUE_LINEAR_GAIN	(V4L2_CID_USER_CCS_BASE + 5)
 #define V4L2_CID_CCS_ANALOGUE_EXPONENTIAL_GAIN	(V4L2_CID_USER_CCS_BASE + 6)
+#define V4L2_CID_CCS_SHADING_CORRECTION		(V4L2_CID_USER_CCS_BASE + 8)
+#define V4L2_CID_CCS_LUMINANCE_CORRECTION_LEVEL	(V4L2_CID_USER_CCS_BASE + 9)
 
 #endif