libcamera: formats: Add toString() methods

Add toString() helpers to pretty print out a V4L2Device or V4L2Subdevice
format.

Reviewed-by: Laurent Pinchart <laurent.pinchart@ideasonboard.com>
Reviewed-by: Kieran Bingham <kieran.bingham@ideasonboard.com>
Signed-off-by: Jacopo Mondi <jacopo@jmondi.org>

src/libcamera/include/v4l2_device.h

@@ -100,6 +100,8 @@ public:
 		uint32_t bpl;
 	} planes[3];
 	unsigned int planesCount;
+
+	const std::string toString() const;
 };
 
 class V4L2Device : protected Loggable

src/libcamera/include/v4l2_subdevice.h

@@ -21,6 +21,8 @@ struct V4L2SubdeviceFormat {
 	uint32_t mbus_code;
 	uint32_t width;
 	uint32_t height;
+
+	const std::string toString() const;
 };
 
 class V4L2Subdevice : protected Loggable

src/libcamera/v4l2_device.cpp

@@ -6,6 +6,8 @@
  */
 
 #include <fcntl.h>
+#include <iomanip>
+#include <sstream>
 #include <string.h>
 #include <sys/ioctl.h>
 #include <sys/mman.h>
@@ -223,6 +225,22 @@ LOG_DEFINE_CATEGORY(V4L2)
  * \brief The number of valid data planes
  */
 
+/**
+ * \brief Assemble and return a string describing the format
+ *
+ * \return A string describing the V4L2DeviceFormat
+ */
+const std::string V4L2DeviceFormat::toString() const
+{
+	std::stringstream ss;
+
+	ss.fill(0);
+	ss << width << "x" << height << "-0x" << std::hex
+	   << std::setw(8) << fourcc;
+
+	return ss.str();
+}
+
 /**
  * \class V4L2Device
  * \brief V4L2Device object and API

src/libcamera/v4l2_subdevice.cpp

@@ -6,6 +6,8 @@
  */
 
 #include <fcntl.h>
+#include <iomanip>
+#include <sstream>
 #include <string.h>
 #include <sys/ioctl.h>
 #include <unistd.h>
@@ -69,6 +71,22 @@ LOG_DEFINE_CATEGORY(V4L2Subdev)
  * \brief The image height in pixels
  */
 
+/**
+ * \brief Assemble and return a string describing the format
+ *
+ * \return A string describing the V4L2SubdeviceFormat
+ */
+const std::string V4L2SubdeviceFormat::toString() const
+{
+	std::stringstream ss;
+
+	ss.fill(0);
+	ss << width << "x" << height << "-0x" << std::hex
+	   << std::setw(4) << mbus_code;
+
+	return ss.str();
+}
+
 /**
  * \class V4L2Subdevice
  * \brief A V4L2 subdevice as exposed by the Linux kernel