chan_simpleusb and chan_usbradio: Should have the ability to automatically assign a compatible usb device

[KB4MDD]

Presently chan_simpleusb and chan_usbradio depend on the user setting the devstr to the correct value. The script asl-find-sound has been created to assist the user in determining the correct value for devstr.

This process is cumbersome for a new user. I proposed that we change these drivers to automatically populate devstr with the first compatible device. The driver already has a list of compatible devices.

The driver would know when to do this by leaving the devstr blank in the installed/shipped simpleusb / usbrradio conf. When we find a blank devstr, we would assign an unassigned compatible device.

When the user modifies the sound levels and saves that configuration, the automatically assigned device string would be saved to the configuration file. (It is already doing that today.)

I will note that 90% or more of our users only have one node and one sound card. If they add a second node, this same operation will work. We find the next unassigned device and associate with the new node.

I think this logic can be added to the hidtread.

[tsawyer]

I like this idea very much and would like to see it in the first release.