On Monday, December 13, 2021 8:31 PM, Ville Syrjälä wrote:
On Sun, Dec 12, 2021 at 11:33:31PM +0800, Lee Shawn C wrote:
According to CEA-861-F chapter 7.5.4. It says "The VSDB shall contain the 3 bytes of the IEEE OUI as well as any additional payload bytes needed." Now DRM driver check HDMI OUI but VSDB payload size at least five bytes. That may caused some HDMI monitors' audio feature can't be enabled. Because of they only have three bytes payload (OUI only) in VSDB.
HDMI 1.4a says "Sinks shall contain an HDMI VSDB minimally containing a 2-byte Source Physical Address field following the 24-bit identifier. ... The minimum value of N (length) is 5 and the maximum value of N is 31."
Do you actually have an EDID that violates that?
Yes! User report when connect to HDMI port on Acer V226HQL. Audio is not working. But windows system did not have the same problem. We found its VSDB just have 3 bytes payload (OUI). Then we share this patch to user then they report audio works properly with this patch.
Best regards, Shawn
Cc: Ville Syrjälä ville.syrjala@linux.intel.com Cc: Adam Jackson ajax@redhat.com Cc: Dave Airlie airlied@redhat.com Signed-off-by: Lee Shawn C shawn.c.lee@intel.com
drivers/gpu/drm/drm_edid.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-)
diff --git a/drivers/gpu/drm/drm_edid.c b/drivers/gpu/drm/drm_edid.c index 12893e7be89b..5aa4a6bf4a13 100644 --- a/drivers/gpu/drm/drm_edid.c +++ b/drivers/gpu/drm/drm_edid.c @@ -4205,7 +4205,7 @@ static bool cea_db_is_hdmi_vsdb(const u8 *db) if (cea_db_tag(db) != VENDOR_BLOCK) return false;
- if (cea_db_payload_len(db) < 5)
if (cea_db_payload_len(db) < 3) return false;
return oui(db[3], db[2], db[1]) == HDMI_IEEE_OUI;
-- 2.31.1
-- Ville Syrjälä Intel