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:
- 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.