[libcamera-devel] [[PATCH v4.1 4/4] ipa: ipu3: awb: Clamp gain values

[Umang Jain]

From: Jean-Michel Hautbois <jeanmichel.hautbois at ideasonboard.com>

The gain values are coded as u3.13 fixed point values, ie they can not
be more than 8. Clamp the values in order to avoid any off limits value
which could make the IPU3 behave in a weird manner.

Signed-off-by: Jean-Michel Hautbois <jeanmichel.hautbois at ideasonboard.com>
Reviewed-by: Kieran Bingham <kieran.bingham at ideasonboard.com>
Signed-off-by: Umang Jain <umang.jain at ideasonboard.com>
Reviewed-by: Umang Jain <umang.jain at ideasonboard.com>
---
 src/ipa/ipu3/algorithms/awb.cpp | 8 ++++++++
 1 file changed, 8 insertions(+)

diff --git a/src/ipa/ipu3/algorithms/awb.cpp b/src/ipa/ipu3/algorithms/awb.cpp
index 1dc27fc9..87a6cc7a 100644
--- a/src/ipa/ipu3/algorithms/awb.cpp
+++ b/src/ipa/ipu3/algorithms/awb.cpp
@@ -353,6 +353,14 @@ void Awb::awbGreyWorld()
 
 	/* Color temperature is not relevant in Grey world but still useful to estimate it :-) */
 	asyncResults_.temperatureK = estimateCCT(sumRed.R, sumRed.G, sumBlue.B);
+
+	/*
+	 * Gain values are unsigned integer value ranging [0, 8) with 13 bit
+	 * fractional part.
+	 */
+	redGain = std::clamp(redGain, 0.0, 65535.0 / 8192);
+	blueGain = std::clamp(blueGain, 0.0, 65535.0 / 8192);
+
 	asyncResults_.redGain = redGain;
 	/* Hardcode the green gain to 1.0. */
 	asyncResults_.greenGain = 1.0;
-- 
2.31.1