[alsa-devel] line-out mute on "phantom" HP jack (Via codec)

Herton Ronaldo Krzesinski herton.krzesinski at canonical.com
Sat Sep 22 01:45:18 CEST 2012


On Via codecs reported on https://bugs.launchpad.net/bugs/1052499, while
investigating the report, it can be seen that on Headphone pin the
plug is not detectable (NO_PRESENCE). It could be that front panel is
AC97 wiring or something else, I don't know. But it makes the jack
detection handling code to add the headphone jack as "phantom", which
makes snd_hda_jack_detect return headphone jack as always present
(commit 80c8bfbe768 is applied/cherry-picked on the reported kernel).

Thus after jacks are added, the automute code will always detect HP as
present, and keep muted all line-outs. The proposed solution following
this is using is_jack_detectable inside via_hp_automute to handle this,
other codecs seem to use also is_jack_detectable at the moment in
similar situations. Other approach could be also to not report presence
on phantom jacks with HP or Line Outs.


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