From 6d8109f4f18f94d86f68de3a49fe8aaf6a1b18bd Mon Sep 17 00:00:00 2001
From: Stefan Klug <stefan.klug@ideasonboard.com>
Date: Tue, 25 Nov 2025 17:28:17 +0100
Subject: [PATCH] libcamera: converter_v4l2_m2m: Add suport for V4L2 requests

To actually use requests with the m2m device, requests need to be
allocated on the underlying media device. This can only be done if the
media device is opened which means acquiring it. Add a function to check
if the m2m device supports requests by acquiring the media device,
asking it and then releasing it again. Also add a function to allocate
requests that acquires the internal media device and releases it after
allocating the requests.

Signed-off-by: Stefan Klug <stefan.klug@ideasonboard.com>
Reviewed-by: Kieran Bingham <kieran.bingham@ideasonboard.com>
---
 .../internal/converter/converter_v4l2_m2m.h   |  7 ++++
 .../converter/converter_v4l2_m2m.cpp          | 34 ++++++++++++++++++-
 2 files changed, 40 insertions(+), 1 deletion(-)

diff --git a/include/libcamera/internal/converter/converter_v4l2_m2m.h b/include/libcamera/internal/converter/converter_v4l2_m2m.h
index 1b2a88c4..bc85bff7 100644
--- a/include/libcamera/internal/converter/converter_v4l2_m2m.h
+++ b/include/libcamera/internal/converter/converter_v4l2_m2m.h
@@ -73,6 +73,11 @@ public:
 	std::pair<Rectangle, Rectangle> inputCropBounds() override { return inputCropBounds_; }
 	std::pair<Rectangle, Rectangle> inputCropBounds(const Stream *stream) override;
 
+	int allocateRequests(unsigned int count,
+			     std::vector<std::unique_ptr<V4L2Request>> *requests);
+
+	bool supportsRequests();
+
 private:
 	class V4L2M2MStream : protected Loggable
 	{
@@ -122,6 +127,8 @@ private:
 	std::map<const Stream *, std::unique_ptr<V4L2M2MStream>> streams_;
 	std::map<FrameBuffer *, unsigned int> queue_;
 	std::pair<Rectangle, Rectangle> inputCropBounds_;
+
+	std::shared_ptr<MediaDevice> media_;
 };
 
 } /* namespace libcamera */
diff --git a/src/libcamera/converter/converter_v4l2_m2m.cpp b/src/libcamera/converter/converter_v4l2_m2m.cpp
index ff11a973..c6153d72 100644
--- a/src/libcamera/converter/converter_v4l2_m2m.cpp
+++ b/src/libcamera/converter/converter_v4l2_m2m.cpp
@@ -9,6 +9,7 @@
 #include "libcamera/internal/converter/converter_v4l2_m2m.h"
 
 #include <algorithm>
+#include <errno.h>
 #include <limits.h>
 #include <memory>
 #include <set>
@@ -266,7 +267,7 @@ void V4L2M2MConverter::V4L2M2MStream::captureBufferReady(FrameBuffer *buffer)
  * \param[in] media The media device implementing the converter
  */
 V4L2M2MConverter::V4L2M2MConverter(std::shared_ptr<MediaDevice> media)
-	: Converter(media)
+	: Converter(media), media_(media)
 {
 	if (deviceNode().empty())
 		return;
@@ -742,6 +743,37 @@ int V4L2M2MConverter::queueBuffers(FrameBuffer *input,
 	return 0;
 }
 
+/**
+ * \copydoc libcamera::MediaDevice::allocateRequests
+ */
+int V4L2M2MConverter::allocateRequests(unsigned int count,
+				       std::vector<std::unique_ptr<V4L2Request>> *requests)
+{
+	/* \todo The acquire() must be moved to the right place. */
+	media_->acquire();
+	if (!media_->busy())
+		LOG(Converter, Error)
+			<< "MediaDevice must be valid.";
+	int ret = media_->allocateRequests(count, requests);
+	media_->release();
+	return ret;
+}
+
+/**
+ * \copydoc libcamera::MediaDevice::supportsRequests
+ */
+bool V4L2M2MConverter::supportsRequests()
+{
+	/* \todo The acquire() must be moved to the right place. */
+	media_->acquire();
+	if (!media_->busy())
+		LOG(Converter, Error)
+			<< "MediaDevice must be valid.";
+	bool ret = media_->supportsRequests();
+	media_->release();
+	return ret;
+}
+
 /*
  * \todo This should be extended to include Feature::Flag to denote
  * what each converter supports feature-wise.