On Tue, Jan 19, 2021 at 10:20:34AM -0800, Doug Kingston wrote:
> I am doing some work setting up some radio data nodes that use USB
> soundcard devices to attach to radios. I am building a system with
> two radios and two identical soundcard devices attached to a Raspberry
> Pi running Raspbian. The devices are discovered at boot time by the
> hid-generic subsystem:
>
> (see dmesg output below)
>
> I am accessing the sound devices from Wine via the ALSA stack. The
> problem I have is that
> the product string is identical for both devices and they show up
> identically to the Windows app ("USB PnP Sound Device").
Why is that bad?
Suppose instead of using a Raspberry Pi, you plugged these two sound
cards into a desktop system that actually was running Windows. How
would they show up then? How would the Windows app handle them?
Whatever this turns out to be, Wine should be able to emulate it.
> I need to
> find a way to alter this string so that they are different.
Why do the strings need to be different? They wouldn't be different in
the desktop-running-Windows case, would they?
> If they
> were processed by udev I might be able to do something there.
They are processed by udev, but I have no idea whether Wine gets this
information from udev or from somewhere else (such as directly from the
sound cards themselves).
> The options seem to be:
> 1) fix at kernel usb discovery
As Greg said, the kernel isn't going to be changed to do this. And even
if you did change your own copy of the kernel, it wouldn't help if Wine
gets the product strings directly from the sound cards.
> 2) somehow fix in the ALSA library (snd_*)
That might be feasible. I don't know much about ALSA's internals.
> 3) fix in Wine (mmsys.drv / winealsa.drv/mmdevdrv.c
That also might work. But in fact, I would expect Wine to handle these
things the same way that native Windows does, whatever that is. So if
Windows doesn't alter the strings, most likely you shouldn't ask Wine to
do so.
> 4) somewhere else?
How about in the app that uses the strings?
> And, we need to do this in a supportable fashion that does not break
> existing users of this subsystem.
>
> Do you have any suggestions?
As Greg mentioned, the app could use the device ID numbers or other
topology information to distinguish the two sound cards, even if the
product strings are identical.
Alan Stern
