pixels: Add function to convert drm format to string

include/pixels.h

@@ -38,3 +38,5 @@ bool fourcc_to_pixman_fmt(pixman_format_code_t* dst, uint32_t src);
 
 bool extract_alpha_mask(uint8_t* dst, const void* src, uint32_t format,
 		size_t len);
+
+const char* drm_format_to_string(uint32_t fmt);

src/pixels.c

@@ -22,6 +22,8 @@
 
 #define POPCOUNT(x) __builtin_popcount(x)
 #define UDIV_UP(a, b) (((a) + (b) - 1) / (b))
+#define XSTR(s) STR(s)
+#define STR(s) #s
 
 void pixel32_to_cpixel(uint8_t* restrict dst,
                        const struct rfb_pixel_format* dst_fmt,
@@ -434,3 +436,37 @@ bool extract_alpha_mask(uint8_t* dst, const void* src, uint32_t format,
 
 	return false;
 }
+
+const char* drm_format_to_string(uint32_t fmt)
+{
+	switch (fmt) {
+#define X(x) case DRM_FORMAT_ ## x: return XSTR(x);
+	X(RGBA1010102) \
+	X(RGBX1010102) \
+	X(BGRA1010102) \
+	X(BGRX1010102) \
+	X(ARGB2101010) \
+	X(XRGB2101010) \
+	X(ABGR2101010) \
+	X(XBGR2101010) \
+	X(RGBA8888) \
+	X(RGBX8888) \
+	X(BGRA8888) \
+	X(BGRX8888) \
+	X(ARGB8888) \
+	X(XRGB8888) \
+	X(ABGR8888) \
+	X(XBGR8888) \
+	X(RGBA4444) \
+	X(RGBX4444) \
+	X(BGRA4444) \
+	X(BGRX4444) \
+	X(ARGB4444) \
+	X(XRGB4444) \
+	X(ABGR4444) \
+	X(XBGR4444) \
+	X(RGB565)
+#undef X
+	}
+	return "UNKNOWN";
+}

test/test-pixels.c

@@ -130,10 +130,25 @@ static bool test_extract_alpha_mask_rgba8888(void)
 	return true;
 }
 
+static bool test_drm_format_to_string(void)
+{
+	if (strcmp(drm_format_to_string(DRM_FORMAT_RGBA8888), "RGBA8888") != 0)
+		return false;
+
+	if (strcmp(drm_format_to_string(DRM_FORMAT_RGBX8888), "RGBX8888") != 0)
+		return false;
+
+	if (strcmp(drm_format_to_string(DRM_FORMAT_RGB565), "RGB565") != 0)
+		return false;
+
+	return true;
+}
+
 int main()
 {
 	bool ok = test_pixel32_to_cpixel_4bpp() &&
 		test_fourcc_to_pixman_fmt() &&
-		test_extract_alpha_mask_rgba8888();
+		test_extract_alpha_mask_rgba8888() &&
+		test_drm_format_to_string();
 	return ok ? 0 : 1;
 }