[Bug 637947] Re: no sound devices on current ES2.0 boards

[Emmet Hikory]

The kernel solution seems to need a machine driver: something akin to
sound/soc/omap/sdp4430.c (either a new file, or adding runtime detection
for the alternate hardware to that file (renaming appropriately, etc.).
Documentation on this lives in Documentation/sound/alsa/soc/machine.txt

In addition to simply providing a base driver to activate the hardware,
such a kernel solution should also strive to provide appropriate
defaults and naming such that as udev discovers the devices, the
information passed to pulseaudio is sufficient for accurate and correct
autoconfiguration.

The userspace solution should be considered only as a fallback.  The
acceptable changes to pulse's daemon.conf will be commited with the
solution to bug #623242 , and are essentially unrelated to this bug
(problems with pulse configuration and codec performance vs. missing
driver).  There is significant interest in not setting flat-volumes =
no, as this is considered to give users the most intuitive response to
use of the audio controls available in the OS.

If the kernel is unable to set a sensible default configuration on
initialisation, the omap4_amixer_config.sh should be replaced with files
in /usr/share/alsa/ as documented in comment #1.  Entries like  "amixer
cset name='Earphone Driver Switch' 1" would become "CTL{name}='Earphone
Driver Switch', CTL{value}=1".  An entry needs to be added to
/usr/share/alsa/init/00main to load this new file conditionally based on
CARDINFO.

The proposed changes to pulse's default.pa are firstly disabling module-
console-kit, which is undesireable, as this is used for such purposes as
allowing user switching and audio at the GDM prompt as well as post-
login; and secondly static loading of various modules: this static
loading is unsuitable as a default for varied hardware, but it is better
to rely on module-udev-detect: if the issues cannot be solved in the
kernel, and appropriate defaults cannot be set for one reason or
another, additional udev rules ought be added to provide pulseaudio with
the appropriate information to load the modules correctly only where
that hardware is present.

-- 
no sound devices on current ES2.0 boards
https://bugs.launchpad.net/bugs/637947
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