[PATCH v6 1/2] libcamera: software_isp: Get black level from the camera helper

[Milan Zamazal]

The black level in software ISP is unconditionally guessed from the
obtained frames.  CameraSensorHelper optionally provides the black level
from camera specifications now.  Let's use the value if available.

If the black level is not available from the given CameraSensorHelper
instance, it's still determined on the fly.

Signed-off-by: Milan Zamazal <mzamazal at redhat.com>
Reviewed-by: Kieran Bingham <kieran.bingham at ideasonboard.com>
Tested-by: Robert Mader <robert.mader at collabora.com>
---
 src/ipa/simple/algorithms/blc.cpp |  6 +++++-
 src/ipa/simple/ipa_context.h      |  4 ++++
 src/ipa/simple/soft_simple.cpp    | 10 ++++++++++
 3 files changed, 19 insertions(+), 1 deletion(-)

diff --git a/src/ipa/simple/algorithms/blc.cpp b/src/ipa/simple/algorithms/blc.cpp
index b9f2aaa6d..a7af2e12c 100644
--- a/src/ipa/simple/algorithms/blc.cpp
+++ b/src/ipa/simple/algorithms/blc.cpp
@@ -24,7 +24,8 @@ BlackLevel::BlackLevel()
 int BlackLevel::configure(IPAContext &context,
 			  [[maybe_unused]] const IPAConfigInfo &configInfo)
 {
-	context.activeState.blc.level = 255;
+	context.activeState.blc.level =
+		context.configuration.black.level.value_or(255);
 	return 0;
 }
 
@@ -34,6 +35,9 @@ void BlackLevel::process(IPAContext &context,
 			 const SwIspStats *stats,
 			 [[maybe_unused]] ControlList &metadata)
 {
+	if (context.configuration.black.level.has_value())
+		return;
+
 	if (frameContext.sensor.exposure == exposure_ &&
 	    frameContext.sensor.gain == gain_) {
 		return;
diff --git a/src/ipa/simple/ipa_context.h b/src/ipa/simple/ipa_context.h
index 3519f20f6..fd121eebe 100644
--- a/src/ipa/simple/ipa_context.h
+++ b/src/ipa/simple/ipa_context.h
@@ -8,6 +8,7 @@
 #pragma once
 
 #include <array>
+#include <optional>
 #include <stdint.h>
 
 #include <libipa/fc_queue.h>
@@ -22,6 +23,9 @@ struct IPASessionConfiguration {
 		int32_t exposureMin, exposureMax;
 		double againMin, againMax, againMinStep;
 	} agc;
+	struct {
+		std::optional<uint8_t> level;
+	} black;
 };
 
 struct IPAActiveState {
diff --git a/src/ipa/simple/soft_simple.cpp b/src/ipa/simple/soft_simple.cpp
index b28c7039f..e96e65bd1 100644
--- a/src/ipa/simple/soft_simple.cpp
+++ b/src/ipa/simple/soft_simple.cpp
@@ -201,6 +201,16 @@ int IPASoftSimple::configure(const IPAConfigInfo &configInfo)
 			(context_.configuration.agc.againMax -
 			 context_.configuration.agc.againMin) /
 			100.0;
+		if (camHelper_->blackLevel().has_value()) {
+			/*
+			 * The black level from camHelper_ is a 16 bit value, software ISP
+			 * works with 8 bit pixel values, both regardless of the actual
+			 * sensor pixel width. Hence we obtain the pixel-based black value
+			 * by dividing the value from the helper by 256.
+			 */
+			context_.configuration.black.level =
+				camHelper_->blackLevel().value() / 256;
+		}
 	} else {
 		/*
 		 * The camera sensor gain (g) is usually not equal to the value written
-- 
2.44.1