libcamera: stream: add initial StreamConfiguration structure

Add an initial StreamConfiguration implementation to hold configuration
data for a single stream of a Camera. In its current form not many
configuration parameters are supported but it's expected the number of
options will grow over time.

At this stage the pixel format is represented as an unsigned int to
allow for easy mapping to the V4L2 API. This might be subject to change
in the future as we finalize how libcamera shall represent pixel
formats.

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

include/libcamera/stream.h

@@ -13,6 +13,12 @@ class Stream final
 {
 };
 
+struct StreamConfiguration {
+	unsigned int width;
+	unsigned int height;
+	unsigned int pixelFormat;
+};
+
 } /* namespace libcamera */
 
 #endif /* __LIBCAMERA_STREAM_H__ */

src/libcamera/stream.cpp

@@ -47,4 +47,30 @@ namespace libcamera {
  * optimal stream for the task.
  */
 
+/**
+ * \struct StreamConfiguration
+ * \brief Configuration parameters for a stream
+ *
+ * The StreamConfiguration structure models all information which can be
+ * configured for a single video stream.
+ */
+
+/**
+ * \var StreamConfiguration::width
+ * \brief Stream width in pixels
+ */
+
+/**
+ * \var StreamConfiguration::height
+ * \brief Stream height in pixels
+ */
+
+/**
+ * \var StreamConfiguration::pixelFormat
+ * \brief Stream pixel format
+ *
+ * This is a little endian four character code representation of the pixel
+ * format described in V4L2 using the V4L2_PIX_FMT_* definitions.
+ */
+
 } /* namespace libcamera */