libcamera: software_isp: Get black level from the camera helper

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@redhat.com>
Reviewed-by: Kieran Bingham <kieran.bingham@ideasonboard.com>
Tested-by: Robert Mader <robert.mader@collabora.com>
Signed-off-by: Kieran Bingham <kieran.bingham@ideasonboard.com>

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;