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media: staging: ipu3-imgu: Fix BNR wb gain documentation

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The documentation states that the BNR factor is a multiplier coded as
u3.13 and with a range of (0, 8). This is not correct, as the isp is
adding 1.0 to the gain applied, ie Pout = { Pin * (1 + Gx) }.

It means that a gain of 1.0 should be coded as 0.

Signed-off-by: Jean-Michel Hautbois <jeanmichel.hautbois@ideasonboard.com>
Reviewed-by: Kieran Bingham <kieran.bingham@ideasonboard.com>
Signed-off-by: Sakari Ailus <sakari.ailus@linux.intel.com>
Signed-off-by: Mauro Carvalho Chehab <mchehab@kernel.org>
This commit is contained in:
Jean-Michel Hautbois 2022-06-17 10:45:19 +02:00 committed by Mauro Carvalho Chehab
parent 39434d42e8
commit 4b7444ff13
1 changed files with 5 additions and 2 deletions
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7
drivers/staging/media/ipu3/include/uapi/intel-ipu3.h
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@ -626,8 +626,11 @@ struct ipu3_uapi_stats_3a {
* @b: white balance gain for B channel.
* @gb: white balance gain for Gb channel.
*
* Precision u3.13, range [0, 8). White balance correction is done by applying
* a multiplicative gain to each color channels prior to BNR.
* For BNR parameters WB gain factor for the three channels [Ggr, Ggb, Gb, Gr].
* Their precision is U3.13 and the range is (0, 8) and the actual gain is
* Gx + 1, it is typically Gx = 1.
*
* Pout = {Pin * (1 + Gx)}.
*/
struct ipu3_uapi_bnr_static_config_wb_gains_config {
__u16 gr;