Bad volume saving behaviour when no sound device is found

[dsd]

The acme-volume-alsa.c code looks for a sound mixer called "Master", falling back on "PCM" if it doesn't exist.

During XO-4 development we have not had either mixer for a while. This has revealed some strange behaviour when we later add a Master/PCM mixer:

If no mixer could be found, acme_volume_alsa_get_volume() returns "0". (It would also return 0 for a mixer where the sound was turned all the way down)

Sugar then saves that 0 to gconf (jarabe.model.sound), and when we later add a kernel with PCM and/or Master mixers, Sugar starts setting volume 0 there.

Not a major issue since it wouldn't hit a "sane" setup. However it has caused some annoyance and confusion during our developer activities right now. It would also affect someone who installs Sugar on a system without a sound card, and then adds a sound card later.