libcamera: request: remove prepare()

The association of buffers to a request can be done directly in
addBuffer() instead of when the request is queued to the camera. Keep
the check that a request contains buffers by moving it to
Camera::queueRequest() where prepare() was previously called.

As a bonus we can remove a friend statement in Request.

Signed-off-by: Niklas Söderlund <niklas.soderlund@ragnatech.se>
Reviewed-by: Laurent Pinchart <laurent.pinchart@ideasonboard.com>

include/libcamera/request.h

@@ -48,10 +48,8 @@ public:
 	bool hasPendingBuffers() const { return !pending_.empty(); }
 
 private:
-	friend class Camera;
 	friend class PipelineHandler;
 
-	int prepare();
 	void complete();
 
 	bool completeBuffer(Buffer *buffer);

src/libcamera/buffer.cpp

@@ -360,7 +360,7 @@ Buffer::Buffer(unsigned int index, const Buffer *metadata)
  * The intended callers of this method are buffer completion handlers that
  * need to associate a buffer to the request it belongs to.
  *
- * A Buffer is associated to a request by Request::prepare() and the
+ * A Buffer is associated to a request by Request::addBuffer() and the
  * association is valid until the buffer completes. The returned request
  * pointer is valid only during that interval.
  *
@@ -397,7 +397,7 @@ void Buffer::cancel()
  * \fn Buffer::setRequest()
  * \brief Set the request this buffer belongs to
  *
- * The intended callers are Request::prepare() and Request::completeBuffer().
+ * The intended callers are Request::addBuffer() and Request::completeBuffer().
  */
 
 } /* namespace libcamera */

src/libcamera/camera.cpp

@@ -810,6 +810,11 @@ int Camera::queueRequest(Request *request)
 	if (!stateIs(CameraRunning))
 		return -EACCES;
 
+	if (request->buffers().empty()) {
+		LOG(Camera, Error) << "Request contains no buffers";
+		return -EINVAL;
+	}
+
 	for (auto const &it : request->buffers()) {
 		Stream *stream = it.first;
 		Buffer *buffer = it.second;
@@ -832,12 +837,6 @@ int Camera::queueRequest(Request *request)
 		buffer->mem_ = &stream->buffers()[buffer->index_];
 	}
 
-	int ret = request->prepare();
-	if (ret) {
-		LOG(Camera, Error) << "Failed to prepare request";
-		return ret;
-	}
-
 	return pipe_->queueRequest(this, request);
 }
 

src/libcamera/request.cpp

@@ -139,6 +139,8 @@ int Request::addBuffer(std::unique_ptr<Buffer> buffer)
 		return -EEXIST;
 	}
 
+	buffer->setRequest(this);
+	pending_.insert(buffer.get());
 	bufferMap_[stream] = buffer.release();
 
 	return 0;
@@ -203,30 +205,6 @@ Buffer *Request::findBuffer(Stream *stream) const
  * otherwise
  */
 
-/**
- * \brief Validate the request and prepare it for the completion handler
- *
- * Requests that contain no buffers are invalid and are rejected.
- *
- * \return 0 on success or a negative error code otherwise
- * \retval -EINVAL The request is invalid
- */
-int Request::prepare()
-{
-	if (bufferMap_.empty()) {
-		LOG(Request, Error) << "Invalid request due to missing buffers";
-		return -EINVAL;
-	}
-
-	for (auto const &pair : bufferMap_) {
-		Buffer *buffer = pair.second;
-		buffer->setRequest(this);
-		pending_.insert(buffer);
-	}
-
-	return 0;
-}
-
 /**
  * \brief Complete a queued request
  *