Heya!
PulseAudio listens for hotplugged audio devices via hal/udev. For each card ALSA creates a bunch of device nodes in /dev. Before PA can open the card it needs to make sure that all devices nodes of the card got properly created. I.e. to make sure that surround sound and SPDIF works it is not sufficient to wait until one PCM device is available, but instead that *all* devices that belong to the card are available, i.e. device nodes created with permissions and ACLs set up correctly. Unfortunately there is no signal from udev/hal/kernel that would tell me explicitly that all subdevices of a specific devices are completely enumerated and device files created for. I have been discussing this a bit with Kay Sievers and we came to the conclusion that a simple fix would be if we could rely that the control (i.e. /dev/snd/controlCxx) device is always the last device to be created for a card.
Looking at the drivers this seems to be generally the case, so I was wondering if I can rely on this? Do all drivers behave like this? Do all drivers expose a control device? Can we officially declare it part of the userspace API that the control device is the last one to be created?
Lennart