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-rw-r--r--src/lib/edid.c28
1 files changed, 21 insertions, 7 deletions
diff --git a/src/lib/edid.c b/src/lib/edid.c
index 800ebdd..e5452a5 100644
--- a/src/lib/edid.c
+++ b/src/lib/edid.c
@@ -23,6 +23,15 @@
#include <stdint.h>
+/*
+ * EDID structure revision 1.1:
+ * http://en.wikipedia.org/w/index.php?title=Extended_display_identification_data&oldid=46295569
+ *
+ * EDID structure revision 1.3:
+ * http://en.wikipedia.org/wiki/Extended_display_identification_data
+ */
+
+
/**
* Parse the EDID of a monitor.
*
@@ -34,25 +43,30 @@
*/
int libgamma_parse_edid(libgamma_crtc_information_t* restrict this, int32_t fields)
{
-#define __test_version(edid, major, minor) (((edid)[18] == major) && ((edid)[19] == minor))
+#define __test_version(edid, major, minor_min, minor_max) \
+ (((edid)[18] == major) && (minor_min <= (edid)[19]) && ((edid)[19] <= minor_max))
#define __m(value) (this->edid[index++] != value)
int error = 0;
int checksum = 0;
size_t i, index = 0;
- /* If the length of the EDID is not 128 bytes, we know that it is not of
- EDID structure revision 1.3, and thus we do not support it. Additionally
+ /* If the length of the EDID is not 128 bytes, we know that it is not of EDID
+ structure revision 1.0–1.3, and thus we do not support it. Additionally
this make sure we do not do segmentation violation on the next test. */
if (this->edid_length != 128)
error = LIBGAMMA_EDID_LENGTH_UNSUPPORTED;
/* Check that the magic number of that of the EDID structure. */
else if (__m(0x00) || __m(0xFF) || __m(0xFF) || __m(0xFF) || __m(0xFF) || __m(0xFF) || __m(0xFF) || __m(0x00))
error = LIBGAMMA_EDID_WRONG_MAGIC_NUMBER;
- /* Check that EDID structure revision 1.3 is used, it is the only version
- we support. It is also by far the most commonly use revision and it is
- currently the newest revision. */
- else if (__test_version(this->edid, 1, 3) == 0)
+ /* Check that EDID structure revision 1.1–1.3 is used, those are the only
+ version we support. EDID structure revision 1.3 is also by far the most
+ commonly use revision and it is currently the newest revision. We know
+ that parsing works for both revision 1.1 and revision 1.3, because of
+ this we assume it is also correct for revision 1.2. However, we are not
+ assuming this for revision 1.0 which appeared in August 1994 and was
+ replaced by revision 1.1 in April 1996. */
+ else if (__test_version(this->edid, 1, 1, 3) == 0)
error = LIBGAMMA_EDID_REVISION_UNSUPPORTED;
/* If we have encountered an error, report it for the fields that require