[RFC,08/19] ipa: rkisp2: algo: bls: Implement black level subtraction

27167 diff mbox series

diff --git a/src/ipa/rkisp2/algorithms/bls.cpp b/src/ipa/rkisp2/algorithms/bls.cpp
new file mode 100644
index 000000000000..aba2b7a867be
--- /dev/null
+++ b/src/ipa/rkisp2/algorithms/bls.cpp
@@ -0,0 +1,154 @@ 
+/* SPDX-License-Identifier: LGPL-2.1-or-later */
+/*
+ * Copyright (C) 2026, Ideas On Board
+ *
+ * RkISP2 Black Level Subtraction control
+ */
+
+#include "bls.h"
+
+#include <linux/videodev2.h>
+
+#include <libcamera/base/log.h>
+
+#include <libcamera/control_ids.h>
+
+/**
+ * \file bls.h
+ */
+
+namespace libcamera {
+
+namespace ipa::rkisp2::algorithms {
+
+/**
+ * \class BlackLevelSubtraction
+ * \brief RkISP2 Black Level Subtraction control
+ *
+ * The pixels output by the camera normally include a black level, because
+ * sensors do not always report a signal level of '0' for black. Pixels at or
+ * below this level should be considered black. To achieve that, the RkISP2 BLS
+ * algorithm subtracts a configurable offset from all pixels.
+ *
+ * The black level can be measured at runtime from an optical dark region of the
+ * camera sensor, or measured during the camera tuning process. The first option
+ * isn't currently supported.
+ *
+ * \todo Add support for black level in the metadata so that we can capture
+ * proper raw images for tuning
+ */
+
+LOG_DEFINE_CATEGORY(RkISP2Bls)
+
+/**
+ * \copydoc libcamera::ipa::Algorithm::init
+ */
+int BlackLevelSubtraction::init(IPAContext &context, const ValueNode &tuningData)
+{
+	std::optional<int16_t> levelRed = tuningData["R"].get<int16_t>();
+	std::optional<int16_t> levelGreenR = tuningData["Gr"].get<int16_t>();
+	std::optional<int16_t> levelGreenB = tuningData["Gb"].get<int16_t>();
+	std::optional<int16_t> levelBlue = tuningData["B"].get<int16_t>();
+	bool tuningHasLevels = levelRed && levelGreenR && levelGreenB && levelBlue;
+
+	auto blackLevel = context.camHelper->blackLevel();
+	if (!blackLevel) {
+		/*
+		 * Not all camera sensor helpers have been updated with black
+		 * levels. Print a warning and fall back to the levels from the
+		 * tuning data to preserve backward compatibility. This should
+		 * be removed once all helpers provide the data.
+		 */
+		LOG(RkISP2Bls, Warning)
+			<< "No black levels provided by camera sensor helper"
+			<< ", please fix";
+
+		blackLevelRed_ = levelRed.value_or(4096);
+		blackLevelGreenR_ = levelGreenR.value_or(4096);
+		blackLevelGreenB_ = levelGreenB.value_or(4096);
+		blackLevelBlue_ = levelBlue.value_or(4096);
+	} else if (tuningHasLevels) {
+		/*
+		 * If black levels are provided in the tuning file, use them to
+		 * avoid breaking existing camera tuning. This is deprecated and
+		 * will be removed.
+		 */
+		LOG(RkISP2Bls, Warning)
+			<< "Deprecated: black levels overwritten by tuning file";
+
+		blackLevelRed_ = *levelRed;
+		blackLevelGreenR_ = *levelGreenR;
+		blackLevelGreenB_ = *levelGreenB;
+		blackLevelBlue_ = *levelBlue;
+	} else {
+		blackLevelRed_ = *blackLevel;
+		blackLevelGreenR_ = *blackLevel;
+		blackLevelGreenB_ = *blackLevel;
+		blackLevelBlue_ = *blackLevel;
+	}
+
+	LOG(RkISP2Bls, Debug)
+		<< "Black levels: red " << blackLevelRed_
+		<< ", green (red) " << blackLevelGreenR_
+		<< ", green (blue) " << blackLevelGreenB_
+		<< ", blue " << blackLevelBlue_;
+
+	return 0;
+}
+
+int BlackLevelSubtraction::configure([[maybe_unused]] IPAContext &context,
+				     [[maybe_unused]] const IPACameraSensorInfo &configInfo)
+{
+	/* \todo Save the cfa */
+
+	return 0;
+}
+
+/**
+ * \copydoc libcamera::ipa::Algorithm::prepare
+ */
+void BlackLevelSubtraction::prepare(IPAContext &context,
+				    const uint32_t frame,
+				    [[maybe_unused]] IPAFrameContext &frameContext,
+				    RkISP2Params *params)
+{
+	if (context.configuration.raw)
+		return;
+
+	if (frame > 1)
+		return;
+
+	auto config = params->block<RkISP2Blocks::Bls>();
+	config.setEnabled(true);
+
+	config->enable_auto = 0;
+
+	/* Scale down to the 12-bit black levels used by the BLS block. */
+	/* \todo Handle cfa properly */
+	config->bls_fixed_val.a = blackLevelRed_ >> 4;
+	config->bls_fixed_val.b = blackLevelGreenR_ >> 4;
+	config->bls_fixed_val.c = blackLevelGreenB_ >> 4;
+	config->bls_fixed_val.d = blackLevelBlue_ >> 4;
+}
+
+/**
+ * \copydoc libcamera::ipa::Algorithm::process
+ */
+void BlackLevelSubtraction::process([[maybe_unused]] IPAContext &context,
+				    [[maybe_unused]] const uint32_t frame,
+				    [[maybe_unused]] IPAFrameContext &frameContext,
+				    [[maybe_unused]] const rkisp2_stats_buffer *stats,
+				    ControlList &metadata)
+{
+	metadata.set(controls::SensorBlackLevels,
+		     { static_cast<int32_t>(blackLevelRed_),
+		       static_cast<int32_t>(blackLevelGreenR_),
+		       static_cast<int32_t>(blackLevelGreenB_),
+		       static_cast<int32_t>(blackLevelBlue_) });
+}
+
+REGISTER_IPA_ALGORITHM(BlackLevelSubtraction, "BlackLevelSubtraction")
+
+} /* namespace ipa::rkisp2::algorithms */
+
+} /* namespace libcamera */
diff --git a/src/ipa/rkisp2/algorithms/bls.h b/src/ipa/rkisp2/algorithms/bls.h
new file mode 100644
index 000000000000..5377ae76a029
--- /dev/null
+++ b/src/ipa/rkisp2/algorithms/bls.h
@@ -0,0 +1,41 @@ 
+/* SPDX-License-Identifier: LGPL-2.1-or-later */
+/*
+ * Copyright (C) 2026, Ideas On Board
+ *
+ * RkISP2 Black Level Subtraction control
+ */
+
+#pragma once
+
+#include "algorithm.h"
+
+namespace libcamera {
+
+namespace ipa::rkisp2::algorithms {
+
+class BlackLevelSubtraction : public Algorithm
+{
+public:
+	BlackLevelSubtraction() = default;
+	~BlackLevelSubtraction() = default;
+
+	int init(IPAContext &context, const ValueNode &tuningData) override;
+	int configure(IPAContext &context,
+		      const IPACameraSensorInfo &configInfo) override;
+	void prepare(IPAContext &context, const uint32_t frame,
+		     IPAFrameContext &frameContext,
+		     RkISP2Params *params) override;
+	void process(IPAContext &context, const uint32_t frame,
+		     IPAFrameContext &frameContext,
+		     const rkisp2_stats_buffer *stats,
+		     ControlList &metadata) override;
+
+private:
+	int16_t blackLevelRed_;
+	int16_t blackLevelGreenR_;
+	int16_t blackLevelGreenB_;
+	int16_t blackLevelBlue_;
+};
+
+} /* namespace ipa::rkisp2::algorithms */
+} /* namespace libcamera */
diff --git a/src/ipa/rkisp2/algorithms/meson.build b/src/ipa/rkisp2/algorithms/meson.build
index 4bb81e48eb01..36996918b39e 100644
--- a/src/ipa/rkisp2/algorithms/meson.build
+++ b/src/ipa/rkisp2/algorithms/meson.build
@@ -1,5 +1,6 @@ 
 # SPDX-License-Identifier: CC0-1.0
 
 rkisp2_ipa_algorithms = files([
+    'bls.cpp',
 ])