libcamera: Use stream roles directly instead of StreamUsage

In order to prepare for an API overhall of the camera configuration
generation, remove the StreamUsage class and replace its uses by stream
roles. The size hints can't be specified anymore, and will be replaced
with an API on the StreamConfiguration to negotiate configuration
parameters with cameras.

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

include/libcamera/stream.h

@@ -8,6 +8,7 @@
 #define __LIBCAMERA_STREAM_H__
 
 #include <string>
+#include <vector>
 
 #include <libcamera/buffer.h>
 #include <libcamera/geometry.h>
@@ -25,48 +26,17 @@ struct StreamConfiguration {
 	std::string toString() const;
 };
 
-class StreamUsage
-{
-public:
-	enum Role {
-		StillCapture,
-		VideoRecording,
-		Viewfinder,
-	};
-
-	Role role() const { return role_; }
-	const Size &size() const { return size_; }
-
-protected:
-	explicit StreamUsage(Role role);
-	StreamUsage(Role role, const Size &size);
-
-private:
-	Role role_;
-	Size size_;
+enum StreamRole {
+	StillCapture,
+	VideoRecording,
+	Viewfinder,
 };
 
+using StreamRoles = std::vector<StreamRole>;
+
 class Stream
 {
 public:
-	class StillCapture : public StreamUsage
-	{
-	public:
-		StillCapture();
-	};
-
-	class VideoRecording : public StreamUsage
-	{
-	public:
-		VideoRecording();
-	};
-
-	class Viewfinder : public StreamUsage
-	{
-	public:
-		Viewfinder(int width, int height);
-	};
-
 	Stream();
 	BufferPool &bufferPool() { return bufferPool_; }
 	const StreamConfiguration &configuration() const { return configuration_; }