[v2] pipeline: simple: Allow buffer counts from 1 to 32
diff mbox series

Message ID 20250927203947.126092-1-robert.mader@collabora.com
State New
Headers show
Series
  • [v2] pipeline: simple: Allow buffer counts from 1 to 32
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Commit Message

Robert Mader Sept. 27, 2025, 8:39 p.m. UTC 
While a default value of 4 buffers appears to be a good default that is
used by other pipelines as well, allowing both higher and lower values
can be desirable, notably for:
1. Video encoding, e.g. encoding multiple buffers in parallel.
2. Clients requesting a single buffer - e.g. in multi-stream scenarios.

Thus allow up to 32 buffers - following the default from vb2 core - while
keeping the default to the previous 4.

While on it:
1. mark the config as adjusted when appropriate.
2. increase the number of internal buffer used by the swISP to 4 as well.
   This has been shipped downstream in postmarketOS for a while and, in
   some cases, seems to improve stability on no-so-great drivers.

Signed-off-by: Robert Mader <robert.mader@collabora.com>

---

Changes since v1 with title "pipeline: simple: Allow buffer counts from 1 to 16 for swISP"
1: Cover all cases, not just the swISP one.
2: Increase maximum to 32 to match vb2 core.
3: Change constant naming to better match similar ones.
4: Bump kNumInternalBuffers to 4.
---
 src/libcamera/pipeline/simple/simple.cpp | 21 ++++++++++++++++++---
 1 file changed, 18 insertions(+), 3 deletions(-)

Patch
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diff --git a/src/libcamera/pipeline/simple/simple.cpp b/src/libcamera/pipeline/simple/simple.cpp
index c816cffc9..23585692c 100644
--- a/src/libcamera/pipeline/simple/simple.cpp
+++ b/src/libcamera/pipeline/simple/simple.cpp
@@ -378,6 +378,9 @@  public:
 	const Transform &combinedTransform() const { return combinedTransform_; }
 
 private:
+	static constexpr unsigned int kNumBuffersDefault = 4;
+	static constexpr unsigned int kNumBuffersMax = 32;
+
 	/*
 	 * The SimpleCameraData instance is guaranteed to be valid as long as
 	 * the corresponding Camera instance is valid. In order to borrow a
@@ -417,7 +420,7 @@  protected:
 	int queueRequestDevice(Camera *camera, Request *request) override;
 
 private:
-	static constexpr unsigned int kNumInternalBuffers = 3;
+	static constexpr unsigned int kNumInternalBuffers = 4;
 
 	struct EntityData {
 		std::unique_ptr<V4L2VideoDevice> video;
@@ -1239,7 +1242,7 @@  CameraConfiguration::Status SimpleCameraConfiguration::validate()
 		    cfg.size != pipeConfig_->captureSize)
 			needConversion_ = true;
 
-		/* Set the stride, frameSize and bufferCount. */
+		/* Set the stride and frameSize. */
 		if (needConversion_) {
 			std::tie(cfg.stride, cfg.frameSize) =
 				data_->converter_
@@ -1262,7 +1265,19 @@  CameraConfiguration::Status SimpleCameraConfiguration::validate()
 			cfg.frameSize = format.planes[0].size;
 		}
 
-		cfg.bufferCount = 4;
+		if (cfg.bufferCount == 0) {
+			LOG(SimplePipeline, Debug)
+				<< "Adjusting bufferCount from " << cfg.bufferCount
+				<< " to " << kNumBuffersDefault;
+			cfg.bufferCount = kNumBuffersDefault;
+			status = Adjusted;
+		} else if (cfg.bufferCount > kNumBuffersMax) {
+			LOG(SimplePipeline, Debug)
+				<< "Adjusting bufferCount from " << cfg.bufferCount
+				<< " to " << kNumBuffersMax;
+			cfg.bufferCount = kNumBuffersMax;
+			status = Adjusted;
+		}
 	}
 
 	return status;