Let's say we do this, then Xirtic also produce PV drivers, and get
assigned their own device ID. Will both of them be visible with
a different device ID for the same device?
Different device ID for the same device isn't possible, a device has
exactly one device ID. I assume you mean two devices visible one with
each ID?
Will windows cope with that?
Or do we need to mediate which device IDs are exposed?
I'd expect that only Xirtic products would provide a device with that
device ID. They may choose to make it mutually exclusive with the
standard device, or they may choose to allow it to co-exist. In the
latter case it is down to them what the behaviour of their drivers is.
In any case this is all down to the people who make that product and
their requirements etc.
For people running Xirtic drivers on non-Xirtic products the rest of my
mail applies -- IOW those users would use a setup.exe which binds those
drivers to the normal device, there is no Xirtic device ID present
anywhere in this scenario.