[alsa-devel] HDMI hot-plug/ELD issues

pl bossart bossart.nospam at gmail.com
Fri Aug 20 00:25:53 CEST 2010

I was testing my pulseaudio AC3 passthrough patch on my new laptop
(all Intel hw, Corei5/IbexPeak, 2.6.35) and noticed a set of issues
with the HDMI output:
1. Playback can happen even if there's no HDMI cable plugged. Or when
I remove the cable, the player isn't notified and keeps sending data
to the driver. This is fine for PCM but I noticed that the receiver
can handle some trouble synchronizing with in AC3-passthrough mode if
the cable is inserted after the playback starts. It would be much
cleaner to allow playback only when there's an actual cable connected,
and to return -ENODEV or something to apps when this happens.
2. It looks like the ELD info is invalid in /proc/asound/cards/. Tried
both with my TV and AV receiver, no luck, all zeroes except for

monitor_present         1
eld_valid               0
connection_type         HDMI
eld_version             [0x0] reserved
edid_version            [0x0] no CEA EDID Timing Extension block present
manufacture_id          0x0
product_id              0x0
port_id                 0x0
support_hdcp            0
support_ai              0
audio_sync_delay        0
speakers                [0xffff] FL/FR LFE FC RL/RR RC FLC/FRC RLC/RRC
sad_count               0

Is there a missing link with the display driver so that this info
would make sense? I remember having a conversation with Fengguang Wu
on this, but I can't remember what the outcome was. Or is this a case
of back luck with broken hardware not sending the legal EDID info?
Thanks for your help on this.

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