libcamera: ipu3: Adjust comment on ImgU configuration

Be more precise in commenting why the ImgU shall not be configured
if only the RAW stream is requested.

As an example, if the ImgU gets unecessary configured:
cam -srole=viewfinder -c2 -C -> WORKS
cam -srole=stillraw -c2 -C -> WORKS
cam -srole=viewfinder -c2 -C -> Failed to queue buffer 0: Invalid argument

Since commit ("libcamera: ipu3: Fix RAW+YUV capture") the ImgU
configuration procedure also correctly implements the assumption that at
least one of the YUV output is being operated. If that's not the case,
as in the RAW-only capture use case, the code tries to access a
non-existing configuration. One more reason to exit early if no YUV
stream is requested.

Reviewed-by: Laurent Pinchart <laurent.pinchart@ideasonboard.com>
Reviewed-by: Niklas Söderlund <niklas.soderlund@ragnatech.se>
Signed-off-by: Jacopo Mondi <jacopo@jmondi.org>

1 files changed, 4 insertions, 3 deletions

diff --git a/src/libcamera/pipeline/ipu3/ipu3.cpp b/src/libcamera/pipeline/ipu3/ipu3.cpp
index f9b65020..4210824b 100644
--- a/src/libcamera/pipeline/ipu3/ipu3.cpp
+++ b/src/libcamera/pipeline/ipu3/ipu3.cpp
@@ -464,9 +464,10 @@ int PipelineHandlerIPU3::configure(Camera *camera, CameraConfiguration *c)
 		return ret;
 
 	/*
-	 * If the ImgU gets configured with proper IF, BDS and GDC sizes, it
-	 * is then expected that frames are dequeued from its main output
-	 * otherwise the system stalls.
+	 * If the ImgU gets configured, its driver seems to expect that
+	 * buffers will be queued to its outputs, as otherwise the next
+	 * capture session that uses the ImgU fails when queueing
+	 * buffers to its input.
 	 *
 	 * If no ImgU configuration has been computed, it means only a RAW
 	 * stream has been requested: return here to skip the ImgU configuration