drm/edid: Fix up partially corrupted headers

We'll still fail the block if it fails the EDID checksum though.

See also: http://bugzilla.redhat.com/534120

Signed-off-by: Adam Jackson <ajax@redhat.com>
Signed-off-by: Dave Airlie <airlied@redhat.com>

diff --git a/drivers/gpu/drm/drm_edid.c b/drivers/gpu/drm/drm_edid.c
index 282008229f068cd62845a6d008eaa24253f822ea..bdea313082366703879bc83c5c93a70922bfa595 100644 (file)
--- a/drivers/gpu/drm/drm_edid.c
+++ b/drivers/gpu/drm/drm_edid.c
@@ -123,16 +123,21 @@ static const u8 edid_header[] = {
  */
 static bool edid_is_valid(struct edid *edid)
 {
-       int i;
+       int i, score = 0;
        u8 csum = 0;
        u8 *raw_edid = (u8 *)edid;
 
-       if (memcmp(edid->header, edid_header, sizeof(edid_header)))
-               goto bad;
-       if (edid->version != 1) {
-               DRM_ERROR("EDID has major version %d, instead of 1\n", edid->version);
+       for (i = 0; i < sizeof(edid_header); i++)
+               if (raw_edid[i] == edid_header[i])
+                       score++;
+
+       if (score == 8) ;
+       else if (score >= 6) {
+               DRM_DEBUG("Fixing EDID header, your hardware may be failing\n");
+               memcpy(raw_edid, edid_header, sizeof(edid_header));
+       } else
                goto bad;
-       }
+
        for (i = 0; i < EDID_LENGTH; i++)
                csum += raw_edid[i];
        if (csum) {
@@ -140,6 +145,11 @@ static bool edid_is_valid(struct edid *edid)
                goto bad;
        }
 
+       if (edid->version != 1) {
+               DRM_ERROR("EDID has major version %d, instead of 1\n", edid->version);
+               goto bad;
+       }
+
        if (edid->revision > 4)
                DRM_DEBUG("EDID minor > 4, assuming backward compatibility\n");