edid-decode: improve image size checks

Carefully check if the image sizes in the base and DisplayID blocks
are consistent.

Signed-off-by: Hans Verkuil <hverkuil-cisco@xs4all.nl>

3 files changed, 52 insertions, 14 deletions

diff --git a/edid-decode.h b/edid-decode.h
index 87cf662..67e681a 100644
--- a/edid-decode.h
+++ b/edid-decode.h
@@ -130,6 +130,7 @@ struct edid_state {
 		warnings = failures = 0;
 		has_cta = has_dispid = false;
 		hide_serial_numbers = false;
+		image_width = image_height = 0;
 
 		// Base block state
 		base.edid_minor = 0;
@@ -178,6 +179,7 @@ struct edid_state {
 			dispid.has_display_parameters = dispid.has_type_1_7 =
 			dispid.has_display_interface_features = false;
 		dispid.block_number = 0;
+		dispid.image_width = dispid.image_height = 0;
 
 		// Block Map block state
 		block_map.saw_block_1 = false;
@@ -202,6 +204,9 @@ struct edid_state {
 	unsigned dtd_max_hsize_mm;
 	unsigned dtd_max_vsize_mm;
 
+	// in 0.1 mm units
+	unsigned image_width, image_height;
+
 	unsigned warnings;
 	unsigned failures;
 
@@ -285,6 +290,8 @@ struct edid_state {
 		bool has_display_interface_features;
 		vec_timings_ext preferred_timings;
 		unsigned native_width, native_height;
+		// in 0.1 mm units
+		unsigned image_width, image_height;
 		unsigned block_number;
 		// Keep track of the found CTA-861 Tag/Extended Tag pairs.
 		// The unsigned value is equal to: (tag) | (OUI enum << 12) or (extended tag) | (tag << 8) | (OUI enum << 12)
diff --git a/parse-base-block.cpp b/parse-base-block.cpp
index 9e2ef4f..048308b 100644
--- a/parse-base-block.cpp
+++ b/parse-base-block.cpp
@@ -1442,6 +1442,8 @@ void edid_state::parse_base_block(const unsigned char *x)
 		printf("    Maximum image size: %u cm x %u cm\n", x[0x15], x[0x16]);
 		base.max_display_width_mm = x[0x15] * 10;
 		base.max_display_height_mm = x[0x16] * 10;
+		image_width = base.max_display_width_mm * 10;
+		image_height = base.max_display_height_mm * 10;
 		if (x[0x15] < 10 || x[0x16] < 10)
 			warn("Dubious maximum image size (%ux%u is smaller than 10x10 cm).\n",
 			     x[0x15], x[0x16]);
@@ -1701,13 +1703,16 @@ void edid_state::check_base_block()
 		 */
 		msg(!out_of_range || base.edid_minor >= 4, "%s", err.c_str());
 	}
-	// The base block will only go up to 255x255 cm for the display size,
-	// so don't fail if one or more image sizes exceeds that.
-	if (!base.max_display_width_mm && !base.max_display_height_mm &&
-	    dtd_max_hsize_mm && dtd_max_vsize_mm &&
-	    dtd_max_hsize_mm <= 2559 && dtd_max_vsize_mm <= 2559) {
-		fail("The DTD image sizes all fit inside 255x255cm, but no display size was set.\n");
-	}
+
+	if ((image_width && dtd_max_hsize_mm >= 10 + image_width / 10) ||
+	    (image_height && dtd_max_vsize_mm >= 10 + image_height / 10))
+		fail("The DTD max image size is %ux%umm, which is larger than the display size %.1fx%.1fmm.\n",
+		     dtd_max_hsize_mm, dtd_max_vsize_mm,
+		     image_width / 10.0, image_height / 10.0);
+	if ((!image_width && dtd_max_hsize_mm) || (!image_height && dtd_max_vsize_mm))
+		fail("The DTD max image size is %ux%umm, but the display size is not specified anywhere.\n",
+		     dtd_max_hsize_mm, dtd_max_vsize_mm);
+
 	// Secondary GTF curves start at a specific frequency. Any legacy timings
 	// that have a positive hsync and negative vsync must be less than that
 	// frequency to avoid confusion.
diff --git a/parse-displayid-block.cpp b/parse-displayid-block.cpp
index ad5099f..0f39830 100644
--- a/parse-displayid-block.cpp
+++ b/parse-displayid-block.cpp
@@ -157,10 +157,18 @@ void edid_state::parse_displayid_parameters(const unsigned char *x)
 	if (!check_displayid_datablock_length(x, 12, 12))
 		return;
 
+	if (dispid.has_display_parameters)
+		fail("Duplicate Display Parameters Data Block.\n");
 	dispid.has_display_parameters = true;
+	dispid.image_width = (x[4] << 8) + x[3];
+	dispid.image_height = (x[6] << 8) + x[5];
+	if (dispid.image_width > image_width ||
+	    dispid.image_height > image_height) {
+		image_width = dispid.image_width;
+		image_height = dispid.image_height;
+	}
 	printf("    Image size: %.1f mm x %.1f mm\n",
-	       ((x[4] << 8) + x[3]) / 10.0,
-	       ((x[6] << 8) + x[5]) / 10.0);
+	       dispid.image_width / 10.0, dispid.image_height / 10.0);
 	unsigned w = (x[8] << 8) + x[7];
 	unsigned h = (x[10] << 8) + x[9];
 	printf("    Display native pixel format: %ux%u\n", w, h);
@@ -1130,17 +1138,29 @@ void edid_state::parse_displayid_parameters_v2(const unsigned char *x,
 {
 	if (!check_displayid_datablock_length(x, 29, 29))
 		return;
+	if (dispid.has_display_parameters)
+		fail("Duplicate Display Parameters Data Block.\n");
+	dispid.has_display_parameters = true;
 
 	unsigned hor_size = (x[4] << 8) + x[3];
 	unsigned vert_size = (x[6] << 8) + x[5];
 
-	dispid.has_display_parameters = true;
-	if (x[1] & 0x80)
-		printf("    Image size: %u mm x %u mm\n",
-		       hor_size, vert_size);
-	else
+	dispid.image_width = hor_size;
+	dispid.image_height = vert_size;
+	if (x[1] & 0x80) {
+		printf("    Image size: %u mm x %u mm\n", hor_size, vert_size);
+		dispid.image_width *= 10;
+		dispid.image_height *= 10;
+	} else {
 		printf("    Image size: %.1f mm x %.1f mm\n",
 		       hor_size / 10.0, vert_size / 10.0);
+	}
+	if (dispid.image_width > image_width ||
+	    dispid.image_height > image_height) {
+		image_width = dispid.image_width;
+		image_height = dispid.image_height;
+	}
+
 	unsigned w = (x[8] << 8) + x[7];
 	unsigned h = (x[10] << 8) + x[9];
 
@@ -1980,4 +2000,10 @@ void edid_state::check_displayid_blocks()
 		     dispid.version >= 0x20 ? "VII" : "I");
 	if (dispid.preferred_timings.empty())
 		fail("DisplayID expects at least one preferred timing.\n");
+	if (dispid.image_width && dispid.image_width < 25600 && dispid.image_height < 25600 &&
+	    (abs((int)dispid.image_width - (int)base.max_display_width_mm * 10) >= 100 ||
+	     abs((int)dispid.image_height - (int)base.max_display_height_mm * 10) >= 100))
+		fail("Image size mismatch: DisplayID: %.1fx%.1fmm Base EDID: %u.0x%u.0mm.\n",
+		     dispid.image_width / 10.0, dispid.image_height / 10.0,
+		     base.max_display_width_mm, base.max_display_height_mm);
 }