libcamera: media_object: Add MediaLink string representations

Various parts of libcamera print the representation of a MediaLink by
inline joining the parts to make a string representation.

This repeated use case can be supported with a common helper to print
the MediaLink in a common manner using the existing toString() and
operator<< overload style to make it easier to report on MediaLink
types.

This implementation will report in the following style:

  'imx283 1-001a'[0] -> 'video-mux'[0]

Reviewed-by: Laurent Pinchart <laurent.pinchart@ideasonboard.com>
Reviewed-by: Stefan Klug <stefan.klug@ideasonboard.com>
Signed-off-by: Kieran Bingham <kieran.bingham@ideasonboard.com>

src/libcamera/media_object.cpp

@@ -146,6 +146,31 @@ MediaLink::MediaLink(const struct media_v2_link *link, MediaPad *source,
 {
 }
 
+/**
+ * \brief Generate a string representation of the MediaLink
+ * \return A string representing the MediaLink
+ */
+std::string MediaLink::toString() const
+{
+	std::stringstream ss;
+	ss << *this;
+
+	return ss.str();
+}
+
+/**
+ * \brief Insert a text representation of a Link into an output stream
+ * \param[in] out The output stream
+ * \param[in] link The MediaLink
+ * \return The output stream \a out
+ */
+std::ostream &operator<<(std::ostream &out, const MediaLink &link)
+{
+	out << *link.source() << " -> " << *link.sink();
+
+	return out;
+}
+
 /**
  * \fn MediaLink::source()
  * \brief Retrieve the link's source pad