libcamera: v4l2_device: Add MediaEntity contructor

Construct a V4L2Device from a MediaEntity device node path. While at
there mark constructor as explicit to avoid copy-construction.

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

src/libcamera/include/v4l2_device.h

@@ -32,10 +32,12 @@ struct V4L2Capability final : v4l2_capability {
 	bool hasStreaming() const { return capabilities & V4L2_CAP_STREAMING; }
 };
 
+class MediaEntity;
 class V4L2Device
 {
 public:
-	V4L2Device(const std::string &devnode);
+	explicit V4L2Device(const std::string &devnode);
+	explicit V4L2Device(const MediaEntity &entity);
 	V4L2Device(const V4L2Device &) = delete;
 	~V4L2Device();
 

src/libcamera/v4l2_device.cpp

@@ -12,6 +12,7 @@
 #include <unistd.h>
 
 #include "log.h"
+#include "media_object.h"
 #include "v4l2_device.h"
 
 /**
@@ -94,6 +95,17 @@ V4L2Device::V4L2Device(const std::string &devnode)
 {
 }
 
+/**
+ * \brief Construct a V4L2Device from a MediaEntity
+ * \param entity The MediaEntity to build the device from
+ *
+ * Construct a V4L2Device from a MediaEntity's device node path.
+ */
+V4L2Device::V4L2Device(const MediaEntity &entity)
+	: V4L2Device(entity.devnode())
+{
+}
+
 V4L2Device::~V4L2Device()
 {
 	close();