libcamera: request: Add Fence to Request::addBuffer()

Add an optional fence parameter to Request::addBuffer() to allow
associating a Fence with a FrameBuffer.

Signed-off-by: Jacopo Mondi <jacopo@jmondi.org>
Reviewed-by: Laurent Pinchart <laurent.pinchart@ideasonboard.com>

include/libcamera/request.h

@@ -17,6 +17,7 @@
 #include <libcamera/base/signal.h>
 
 #include <libcamera/controls.h>
+#include <libcamera/fence.h>
 
 namespace libcamera {
 
@@ -51,7 +52,8 @@ public:
 	ControlList &controls() { return *controls_; }
 	ControlList &metadata() { return *metadata_; }
 	const BufferMap &buffers() const { return bufferMap_; }
-	int addBuffer(const Stream *stream, FrameBuffer *buffer);
+	int addBuffer(const Stream *stream, FrameBuffer *buffer,
+		      std::unique_ptr<Fence> fence = nullptr);
 	FrameBuffer *findBuffer(const Stream *stream) const;
 
 	uint32_t sequence() const;

src/libcamera/request.cpp

@@ -14,6 +14,7 @@
 
 #include <libcamera/camera.h>
 #include <libcamera/control_ids.h>
+#include <libcamera/fence.h>
 #include <libcamera/framebuffer.h>
 #include <libcamera/stream.h>
 
@@ -294,6 +295,7 @@ void Request::reuse(ReuseFlag flags)
  * \brief Add a FrameBuffer with its associated Stream to the Request
  * \param[in] stream The stream the buffer belongs to
  * \param[in] buffer The FrameBuffer to add to the request
+ * \param[in] fence The optional fence
  *
  * A reference to the buffer is stored in the request. The caller is responsible
  * for ensuring that the buffer will remain valid until the request complete
@@ -302,11 +304,27 @@ void Request::reuse(ReuseFlag flags)
  * A request can only contain one buffer per stream. If a buffer has already
  * been added to the request for the same stream, this function returns -EEXIST.
  *
+ * A Fence can be optionally associated with the \a buffer.
+ *
+ * When a valid Fence is provided to this function, \a fence is moved to \a
+ * buffer and this Request will only be queued to the device once the
+ * fences of all its buffers have been correctly signalled.
+ *
+ * If the \a fence associated with \a buffer isn't signalled, the request will
+ * fail after a timeout. The buffer will still contain the fence, which
+ * applications must retrieve with FrameBuffer::releaseFence() before the buffer
+ * can be reused in another request. Attempting to add a buffer that still
+ * contains a fence to a request will result in this function returning -EEXIST.
+ *
+ * \sa FrameBuffer::releaseFence()
+ *
  * \return 0 on success or a negative error code otherwise
  * \retval -EEXIST The request already contains a buffer for the stream
+ *  or the buffer still references a fence
  * \retval -EINVAL The buffer does not reference a valid Stream
  */
-int Request::addBuffer(const Stream *stream, FrameBuffer *buffer)
+int Request::addBuffer(const Stream *stream, FrameBuffer *buffer,
+		       std::unique_ptr<Fence> fence)
 {
 	if (!stream) {
 		LOG(Request, Error) << "Invalid stream reference";
@@ -323,6 +341,18 @@ int Request::addBuffer(const Stream *stream, FrameBuffer *buffer)
 	_d()->pending_.insert(buffer);
 	bufferMap_[stream] = buffer;
 
+	/*
+	 * Make sure the fence has been extracted from the buffer
+	 * to avoid waiting on a stale fence.
+	 */
+	if (buffer->_d()->fence()) {
+		LOG(Request, Error) << "Can't add buffer that still references a fence";
+		return -EEXIST;
+	}
+
+	if (fence && fence->isValid())
+		buffer->_d()->setFence(std::move(fence));
+
 	return 0;
 }