[libcamera-devel] [RFC PATCH v1 06/12] libcamera: framebuffer: Add a function to check if planes are contiguous

[Laurent Pinchart]

Multi-planar frame buffers can store their planes contiguously in
memory, or split them in discontiguous memory areas. Add a private
function to check in which of these two categories the frame buffer
belongs. This will be used to correctly handle the differences between
the V4L2 single and multi planar APIs.

Signed-off-by: Laurent Pinchart <laurent.pinchart at ideasonboard.com>
---
 include/libcamera/internal/framebuffer.h |  2 ++
 src/libcamera/framebuffer.cpp            | 45 +++++++++++++++++++++++-
 2 files changed, 46 insertions(+), 1 deletion(-)

diff --git a/include/libcamera/internal/framebuffer.h b/include/libcamera/internal/framebuffer.h
index 606aed2b4782..cd33c295466e 100644
--- a/include/libcamera/internal/framebuffer.h
+++ b/include/libcamera/internal/framebuffer.h
@@ -21,9 +21,11 @@ public:
 	Private();
 
 	void setRequest(Request *request) { request_ = request; }
+	bool isContiguous() const { return isContiguous_; }
 
 private:
 	Request *request_;
+	bool isContiguous_;
 };
 
 } /* namespace libcamera */
diff --git a/src/libcamera/framebuffer.cpp b/src/libcamera/framebuffer.cpp
index 53ef89bf458f..99265b44da43 100644
--- a/src/libcamera/framebuffer.cpp
+++ b/src/libcamera/framebuffer.cpp
@@ -106,7 +106,7 @@ LOG_DEFINE_CATEGORY(Buffer)
  */
 
 FrameBuffer::Private::Private()
-	: request_(nullptr)
+	: request_(nullptr), isContiguous_(true)
 {
 }
 
@@ -120,6 +120,17 @@ FrameBuffer::Private::Private()
  * handlers, it is called by the pipeline handlers themselves.
  */
 
+/**
+ * \fn FrameBuffer::Private::isContiguous()
+ * \brief Check if the frame buffer stores planes contiguously in memory
+ *
+ * Multi-planar frame buffers can store their planes contiguously in memory, or
+ * split them in discontiguous memory areas. This function checks in which of
+ * these two categories the frame buffer belongs.
+ *
+ * \return True if the planes are stored contiguously in memory, false otherwise
+ */
+
 /**
  * \class FrameBuffer
  * \brief Frame buffer data and its associated dynamic metadata
@@ -199,9 +210,41 @@ FrameBuffer::FrameBuffer(const std::vector<Plane> &planes, unsigned int cookie)
 	: Extensible(std::make_unique<Private>()), planes_(planes),
 	  cookie_(cookie)
 {
+	unsigned int offset = 0;
+
 	/* \todo Remove the assertions after sufficient testing */
 	for (const auto &plane : planes_)
 		ASSERT(plane.offset != Plane::kInvalidOffset);
+
+	bool isContiguous = true;
+	ino_t inode = 0;
+
+	for (const auto &plane : planes_) {
+		if (plane.offset != offset) {
+			isContiguous = false;
+			break;
+		}
+
+		/*
+		 * Two different dmabuf file descriptors may still refer to the
+		 * same dmabuf instance. Check this using inodes.
+		 */
+		if (plane.fd.fd() != planes_[0].fd.fd()) {
+			if (!inode)
+				inode = planes_[0].fd.inode();
+			if (plane.fd.inode() != inode) {
+				isContiguous = false;
+				break;
+			}
+		}
+
+		offset += plane.length;
+	}
+
+	LOG(Buffer, Debug)
+		<< "Buffer is " << (isContiguous ? "not " : "") << "contiguous";
+
+	_d()->isContiguous_ = isContiguous;
 }
 
 /**
-- 
Regards,

Laurent Pinchart