ipa: rkisp1: Introduce AWB

The RkISP1 ISP calculates a mean value for Y, Cr and Cb at each frame.
There is a RGB mode which could theoretically give us the values for R,
G and B directly, but it seems to be failing right now.

Convert those values into R, G and B and estimate the gain to apply in a
grey world.

Signed-off-by: Jean-Michel Hautbois <jeanmichel.hautbois@ideasonboard.com>
Tested-by: Peter Griffin <peter.griffin@linaro.org>
Reviewed-by: Laurent Pinchart <laurent.pinchart@ideasonboard.com>

src/ipa/rkisp1/algorithms/awb.h

@@ -0,0 +1,33 @@
+/* SPDX-License-Identifier: LGPL-2.1-or-later */
+/*
+ * Copyright (C) 2021-2022, Ideas On Board
+ *
+ * awb.h - AWB control algorithm
+ */
+
+#pragma once
+
+#include <linux/rkisp1-config.h>
+
+#include "algorithm.h"
+
+namespace libcamera {
+
+namespace ipa::rkisp1::algorithms {
+
+class Awb : public Algorithm
+{
+public:
+	Awb() = default;
+	~Awb() = default;
+
+	int configure(IPAContext &context, const IPACameraSensorInfo &configInfo) override;
+	void prepare(IPAContext &context, rkisp1_params_cfg *params) override;
+	void process(IPAContext &context, const rkisp1_stat_buffer *stats) override;
+
+private:
+	uint32_t estimateCCT(double red, double green, double blue);
+};
+
+} /* namespace ipa::rkisp1::algorithms */
+} /* namespace libcamera */