mjhjmtu

The target kernel is: 2.6.35.14 (old) and its running on an embedded platform and the codec is a wm8753.

I am trying to understand how the alsactl system works. I found a file asound.play @ etc/alsa and this is the configuration file the man pages refer to. I am not sure why mine is called asound.play instead of asound.state but running:

#alsactl init
#alsactl -f /etc/alsa/asound.play store

will default the asound.play file. With the customized version sound works but it doesn't with the default configuration. Here is an excerpt from the asound.play file for a default configuration and the custom configuration. Keep in mind this is just one control block of 85:

Default:

control.1 
 comment.access 'read write'
 comment.type INTEGER
 comment.count 2
 comment.range '0 - 255'
 comment.dbmin -12750
 comment.dbmax 0
 iface MIXER
 name 'PCM Volume'
 value.0 215
 value.1 215
 

custom:

control.1 
 comment.access 'read write'
 comment.type INTEGER
 comment.count 2
 comment.range '0 - 255'
 iface MIXER
 name 'PCM Volume'
 value.0 250
 value.1 250
 

It isn't obvious to me how the person who originally customized the file knew that she/he needed to get rid of comment.dbmin and dbmax. So how might one go about figuring out how they should be customizing this file so that sound works? Guess and check?

I'd guess that the dbmin/dbmax comments are missing because that file was generated with an older version of the driver that did not yet have dB information.
Anyway, comments are ignored by alsactl restore, so this does not matter.

The iface and name entries identify a mixer control; the value values specify the value(s) of that control.

To get the sound to work, you have to know how these mixer controls affect the hardware. Obviously, whoever created those customized settings did know.