Re: [PATCH 1/1] Add virtio-input driver.

  Hi,

quoted

There will also be pass-through support, i.e. qemu
opening /dev/input/event<nr> and forwarding everything to the guest.
How should that be handled best?  Copy all four from the host?  Even
though the bustype is BUS_USB?  Not sure this actually improves things
because the guest can match the device, or whenever this confuses apps
due to BUS_USB being applied to virtio devices ...

Lemme give an example: We have databases in user-space, that allow
applications to figure out the mouse DPI values of a device. Those
databases match on all four, bus+vid+pid+ver (sometimes even more,
like name and dmi). If one of those is not forwarded, it will not be
detected.

Ok, so forward as much as possible.

I'd like to see all four forwarded from the host. I'd be fine with
"bus" being set to VIRTUAL, but I'm not sure why that would be a good
thing to do?

I think for the emulated devices it's fine to use VIRTUAL.

For the passthrough case suspected we could confuse apps because ->phys
points to a virtio device whereas ->type says "I'm usb".

But at least the device database probably doesn't care much about the
physical path I guess, because the mouse is the same no matter which usb
port I plug it in, correct?

cheers,
  Gerd