Message ID | 20190902131546.4691-1-ville.syrjala@linux.intel.com (mailing list archive) |
---|---|
State | New, archived |
Headers | show |
Series | [1/2] drm/edid: Don't look for CEA data blocks in CEA ext block rev < 3 | expand |
Hi Ville, On Mon, 2 Sep 2019 16:15:45 +0300, Ville Syrjala wrote: > From: Ville Syrjälä <ville.syrjala@linux.intel.com> > > CEA ext block revisions 1 and 2 do not contain the data block > collection. Instead that section of the extension block is > marked as reserved for 8 byte timing descriptors. Revision 3 > changed it to contain the CEA data block collection instead. > > Most places that iterate the data blocks already check for > revision >= 3, but drm_detect_hdmi_monitor() and > drm_detect_monitor_audio() do not. So in theory when encountering > rev 1 or 2 CEA extension block they could end up misinterpreting > whatever data is in the reserved section as CEA data blocks. > > Let's have cea_db_offsets() do the revision check so that the > callers don't even have worry about it. > > Cc: Jean Delvare <jdelvare@suse.de> > Signed-off-by: Ville Syrjälä <ville.syrjala@linux.intel.com> > --- > drivers/gpu/drm/drm_edid.c | 3 +++ > 1 file changed, 3 insertions(+) > > diff --git a/drivers/gpu/drm/drm_edid.c b/drivers/gpu/drm/drm_edid.c > index 82a4ceed3fcf..7b3072fc550b 100644 > --- a/drivers/gpu/drm/drm_edid.c > +++ b/drivers/gpu/drm/drm_edid.c > @@ -3690,6 +3690,9 @@ cea_revision(const u8 *cea) > static int > cea_db_offsets(const u8 *cea, int *start, int *end) > { > + if (cea_revision(cea) < 3) > + return -ENOTSUPP; > + > /* DisplayID CTA extension blocks and top-level CEA EDID > * block header definitions differ in the following bytes: > * 1) Byte 2 of the header specifies length differently, Reviewed-by: Jean Delvare <jdelvare@suse.de> I like it, but then we need a subsequent patch to remove the now redundant checks in add_cea_modes(), drm_edid_to_eld(), drm_edid_to_sad() and drm_edid_to_speaker_allocation(). These last 2 functions are the ones my own patch modifies, so some care is needed. If cea_db_offsets() now returns an error when CEA revisions < 3, then these functions want to return 0 in that case (otherwise you effectively undo the change I proposed). By the way, both functions issue a debug message "SAD: invalid data block offsets" when cea_db_offsets() returns an error, which becomes misleading after your change. I think we want to move this message inside cea_db_offsets() and only print it in the -ERANGE case.
diff --git a/drivers/gpu/drm/drm_edid.c b/drivers/gpu/drm/drm_edid.c index 82a4ceed3fcf..7b3072fc550b 100644 --- a/drivers/gpu/drm/drm_edid.c +++ b/drivers/gpu/drm/drm_edid.c @@ -3690,6 +3690,9 @@ cea_revision(const u8 *cea) static int cea_db_offsets(const u8 *cea, int *start, int *end) { + if (cea_revision(cea) < 3) + return -ENOTSUPP; + /* DisplayID CTA extension blocks and top-level CEA EDID * block header definitions differ in the following bytes: * 1) Byte 2 of the header specifies length differently,