libcamera: pipeline: simple: Setup links in the context of sink entities

To setup links the pipeline handler iterates over all entities in the
pipeline and disables all links but the ones we want to enable. Some
entities don't allow multiple sink links to be enabled, so the iteration
needs to be based on sink entities, disabling all their links first and
then enabling the sink link that is part of the pipeline.

The loop implementation iterates over all Entity instances, and uses
their source link to locate the MediaEntity for the connected sink. The
sink entity is then processed in the context of the source's loop
iteration. This prevents the code from being able to access extra
information about the sink entity, as we only have access to the
MediaEntity, not the Entity.

To prepare for subdev routing support that will require accessing
additional entity information, refactor the loop to process the sink
entity in the context of its Entity instance.

Signed-off-by: Laurent Pinchart <laurent.pinchart@ideasonboard.com>

1 files changed, 17 insertions, 7 deletions

diff --git a/src/libcamera/pipeline/simple/simple.cpp b/src/libcamera/pipeline/simple/simple.cpp
index 41b52699..8c3fbc9e 100644
--- a/src/libcamera/pipeline/simple/simple.cpp
+++ b/src/libcamera/pipeline/simple/simple.cpp
@@ -553,15 +553,23 @@ int SimpleCameraData::setupLinks()
 	 * multiple sink links to be enabled together, even on different sink
 	 * pads. We must thus start by disabling all sink links (but the one we
 	 * want to enable) before enabling the pipeline link.
+	 *
+	 * The entities_ list stores entities along with their source link. We
+	 * need to process the link in the context of the sink entity, so
+	 * record the source link of the current entity as the sink link of the
+	 * next entity, and skip the first entity in the loop.
 	 */
+	MediaLink *sinkLink = nullptr;
+
 	for (SimpleCameraData::Entity &e : entities_) {
-		if (!e.sourceLink)
-			break;
+		if (!sinkLink) {
+			sinkLink = e.sourceLink;
+			continue;
+		}
 
-		MediaEntity *remote = e.sourceLink->sink()->entity();
-		for (MediaPad *pad : remote->pads()) {
+		for (MediaPad *pad : e.entity->pads()) {
 			for (MediaLink *link : pad->links()) {
-				if (link == e.sourceLink)
+				if (link == sinkLink)
 					continue;
 
 				if ((link->flags() & MEDIA_LNK_FL_ENABLED) &&
@@ -573,11 +581,13 @@ int SimpleCameraData::setupLinks()
 			}
 		}
 
-		if (!(e.sourceLink->flags() & MEDIA_LNK_FL_ENABLED)) {
-			ret = e.sourceLink->setEnabled(true);
+		if (!(sinkLink->flags() & MEDIA_LNK_FL_ENABLED)) {
+			ret = sinkLink->setEnabled(true);
 			if (ret < 0)
 				return ret;
 		}
+
+		sinkLink = e.sourceLink;
 	}
 
 	return 0;