Bug 101201

This is a bit hard to describe. I'd really like to see a way to manually set priorities on sinks. I recently got a portable DAC, and I wanted to use it when plugged in and fall back on module-combine-sink otherwise - mostly because I often use a program that cannot handle changing sinks. This however means I needed my priorities to be correctly ordered. After fixing the identification of my DAC on the udev side, and switching to running a git build to have recent fixes like https://bugs.freedesktop.org/show_bug.cgi?id=99222, I ran into that I wanted the module-combine-sink sink to be above my internal card but below my DAC. I solved this for now with `load-module module-combine-sink sink_properties='device.class="sound" device.form_factor="speaker"'
`, but that's faking out the priority setting to get the right order, not doing it any sort of "right".

I'm imagining adding a proplist entry of some naming that lets you outright set the priority, and there would be a check at the start of pa_device_init_priority in sink.c that would outright set the priority if it was a valid value. I'd like to know, though, how that sounds, what people think, ideas about the name, if there's anything big I might be missing, before I try to work on a patch.