libcamera: camera: Add support for stream usages

Instead of requesting the default configuration for a set of streams
where the application has to figure out which streams provided by the
camera is best suited for its intended usage, have the library figure
this out by using stream usages.

The application asks the library for a list of streams and a suggested
default configuration for them by supplying a list of stream usages.
Once the list is retrieved the application can fine-tune the returned
configuration and then try to apply it to the camera.

Currently no pipeline handler is prepared to handle stream usages but
nor did it make use of the list of Stream IDs which was the previous
interface. The main reason for this is that all cameras currently only
provide one stream each. This will still be the case but the API will be
prepared to expand both pipeline handlers and applications to support
streams usages.

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

1 files changed, 10 insertions, 20 deletions

diff --git a/src/libcamera/camera.cpp b/src/libcamera/camera.cpp
index 8ee9cc08..63fde0ff 100644
--- a/src/libcamera/camera.cpp
+++ b/src/libcamera/camera.cpp
@@ -345,33 +345,23 @@ const std::set<Stream *> &Camera::streams() const
 }
 
 /**
- * \brief Retrieve a group of stream configurations
- * \param[in] streams A map of stream IDs and configurations to setup
+ * \brief Retrieve a group of stream configurations according to stream usages
+ * \param[in] usages A list of stream usages
  *
- * Retrieve the camera's configuration for a specified group of streams. The
- * caller can specifies which of the camera's streams to retrieve configuration
- * from by populating \a streams.
+ * Retrieve configuration for a set of desired usages. The caller specifies a
+ * list of stream usages and the camera returns a map of suitable streams and
+ * their suggested default configurations.
  *
- * The easiest way to populate the array of streams to fetch configuration from
- * is to first retrieve the camera's full array of stream with streams() and
- * then potentially trim it down to only contain the streams the caller
- * are interested in.
- *
- * \return A map of successfully retrieved stream IDs and configurations or an
- * empty list on error.
+ * \return A map of streams to configurations if the requested usages can be
+ * satisfied, or an empty map otherwise
  */
 std::map<Stream *, StreamConfiguration>
-Camera::streamConfiguration(std::set<Stream *> &streams)
+Camera::streamConfiguration(const std::vector<StreamUsage> &usages)
 {
-	if (disconnected_ || !streams.size())
+	if (disconnected_ || !usages.size() || usages.size() > streams_.size())
 		return std::map<Stream *, StreamConfiguration>{};
 
-	for (Stream *stream : streams) {
-		if (streams_.find(stream) == streams_.end())
-			return std::map<Stream *, StreamConfiguration>{};
-	}
-
-	return pipe_->streamConfiguration(this, streams);
+	return pipe_->streamConfiguration(this, usages);
 }
 
 /**