[libcamera-devel] [RFC PATCH] ipa: ipu3: Retain request controls in the IPA

[Kieran Bingham]

To ensure consistency in processing control lists, an application does
not have to continually set controls that were already set, but not
expected to change.

To ensure we keep that state, merge incoming request control lists with
a stored ControlList that is owned by the IPA and store the state of
that merged list to the per frame FrameContext so that algorithms know
the full expected control state at that time.

Signed-off-by: Kieran Bingham <kieran.bingham at ideasonboard.com>

---

RFC:

1)

If ControlList.update() were implemented like .merge, but with
overriding existing values, instead of leaving them then this could be
simplified to :

+	retainedControls_.update(controls);
+	context_.frameContexts[frame % kMaxFrameContexts] = { frame, std::copy(retainedControls_) };

Not yet sure if that's more efficient or if it doesn't make much
difference.

2)

This will not support triggered controls that are set once to
'fire'... Do we have / plan to have any of those?

3)

Do we want to keep both a delta control list (the incoming controls) as
well as the merged/retained list for full state so IPA's can know if
something was changed?

Signed-off-by: Kieran Bingham <kieran.bingham at ideasonboard.com>
---
 src/ipa/ipu3/ipu3.cpp | 23 ++++++++++++++++++++++-
 1 file changed, 22 insertions(+), 1 deletion(-)

diff --git a/src/ipa/ipu3/ipu3.cpp b/src/ipa/ipu3/ipu3.cpp
index 2f6bb672f7bb..89fc34f86e46 100644
--- a/src/ipa/ipu3/ipu3.cpp
+++ b/src/ipa/ipu3/ipu3.cpp
@@ -176,6 +176,9 @@ private:
 
 	/* Local parameter storage */
 	struct IPAContext context_;
+
+	/* Control retention to maintain mode states */
+	ControlList retainedControls_;
 };
 
 /**
@@ -456,6 +459,8 @@ int IPAIPU3::configure(const IPAConfigInfo &configInfo,
 
 	/* Clean IPAActiveState at each reconfiguration. */
 	context_.activeState = {};
+	retainedControls_.clear();
+
 	IPAFrameContext initFrameContext;
 	context_.frameContexts.fill(initFrameContext);
 
@@ -617,8 +622,24 @@ void IPAIPU3::processStatsBuffer(const uint32_t frame,
  */
 void IPAIPU3::queueRequest(const uint32_t frame, const ControlList &controls)
 {
+	/*
+	 * Controls are retained, to ensure any mode updates are persistant.
+	 * We merge them into our class control storage before assigning to
+	 * the frame context.
+	 *
+	 * \todo This will not support trigger controls and may need rework if
+	 *	 we add any to prevent continually retriggering.
+	 *
+	 * \todo We may wish to store both the full merged control list, as well
+	 *	 as the delta (\a controls) to facilitate algorithms identifying
+	 *	 when things have changed.
+	 */
+	ControlList mergeControls = controls;
+	mergeControls.merge(retainedControls_);
+	retainedControls_ = mergeControls;
+
 	/* \todo Start processing for 'frame' based on 'controls'. */
-	context_.frameContexts[frame % kMaxFrameContexts] = { frame, controls };
+	context_.frameContexts[frame % kMaxFrameContexts] = { frame, std::move(mergeControls) };
 }
 
 /**
-- 
2.25.1