On Mon, Dec 13, 2021 at 12:42:22PM +0000, Lee, Shawn C wrote: > > 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. Hrm. This deserves a comment then since it clearly violates the spec. Also a link to the bug if you have one would be nice to include here. > > Best regards, > Shawn > > >> > >> Cc: Ville Syrjälä <ville.syrjala@xxxxxxxxxxxxxxx> > >> Cc: Adam Jackson <ajax@xxxxxxxxxx> > >> Cc: Dave Airlie <airlied@xxxxxxxxxx> > >> Signed-off-by: Lee Shawn C <shawn.c.lee@xxxxxxxxx> > >> --- > >> 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 > > -- Ville Syrjälä Intel
