libcamera: v4l2PixelFormat: Replace hex with fourCC

Print fourCC characters instead of the hex value in toString() as they are
more informative. Also, write the tests for this in formats.cpp

Signed-off-by: Kaaira Gupta <kgupta@es.iitr.ac.in>
Reviewed-by: Kieran Bingham <kieran.bingham@ideasonboard.com>
Reviewed-by: Laurent Pinchart <laurent.pinchart@ideasonboard.com>
Signed-off-by: Kieran Bingham <kieran.bingham@ideasonboard.com>

2 files changed, 40 insertions, 3 deletions

diff --git a/src/libcamera/v4l2_videodevice.cpp b/src/libcamera/v4l2_videodevice.cpp
index b778181a..eb33a68e 100644
--- a/src/libcamera/v4l2_videodevice.cpp
+++ b/src/libcamera/v4l2_videodevice.cpp
@@ -336,9 +336,23 @@ bool V4L2BufferCache::Entry::operator==(const FrameBuffer &buffer) const
  */
 std::string V4L2PixelFormat::toString() const
 {
-	char str[11];
-	snprintf(str, 11, "0x%08x", fourcc_);
-	return str;
+	if (fourcc_ == 0)
+		return "<INVALID>";
+
+	char ss[8] = { static_cast<char>(fourcc_ & 0x7f),
+		       static_cast<char>((fourcc_ >> 8) & 0x7f),
+		       static_cast<char>((fourcc_ >> 16) & 0x7f),
+		       static_cast<char>((fourcc_ >> 24) & 0x7f) };
+
+	for (unsigned int i = 0; i < 4; i++) {
+		if (!isprint(ss[i]))
+			ss[i] = '.';
+	}
+
+	if (fourcc_ & (1 << 31))
+		strcat(ss, "-BE");
+
+	return ss;
 }
 
 /**
diff --git a/test/v4l2_videodevice/formats.cpp b/test/v4l2_videodevice/formats.cpp
index d504d178..a7421421 100644
--- a/test/v4l2_videodevice/formats.cpp
+++ b/test/v4l2_videodevice/formats.cpp
@@ -8,6 +8,7 @@
 #include <iostream>
 #include <limits.h>
 
+#include "utils.h"
 #include "v4l2_videodevice.h"
 
 #include "v4l2_videodevice_test.h"
@@ -47,6 +48,28 @@ protected:
 			return TestFail;
 		}
 
+		std::vector<std::pair<uint32_t, const char *>> formats{
+			{ V4L2_PIX_FMT_YUYV, "YUYV" },
+			{ 0, "<INVALID>" },
+			{ v4l2_fourcc(0, 1, 2, 3), "...." },
+			{ V4L2_PIX_FMT_Y16_BE, "Y16 -BE" }
+		};
+
+		for (const auto &format : formats) {
+			if (V4L2PixelFormat(format.first).toString() != format.second) {
+				cerr << "Failed to convert V4L2PixelFormat"
+				     << utils::hex(format.first) << "to string"
+				     << endl;
+				return TestFail;
+			}
+		}
+
+		if (V4L2PixelFormat().toString() != "<INVALID>") {
+			cerr << "Failed to convert default V4L2PixelFormat to string"
+			     << endl;
+			return TestFail;
+		}
+
 		return TestPass;
 	}
 };