Re: Xen Virtual Keyboard modalias breaking uevents

[Dmitry Torokhov <dmitry.torokhov@xxxxxxxxx>]

On Thu, Apr 29, 2021 at 08:11:03PM -0400, Phillip Susi wrote:
> 
> Dmitry Torokhov writes:
> 
> > Not every keyboard, but all keycodes above KEY_MIN_INTERESTING which is
> > KEY_MUTE, so that interested handlers could match on devices they are
> > interested in without first opening them or poking through sysfs.
> 
> /Shouldn't/ they be reading sysfs attributes to find that information
> out though?  Isn't modalias there to help modprobe find the right module
> that wants to bind to this device, which doesn't happen for input
> devices?  If user space is looking at this information then isn't it
> getting it by reading from sysfs anyway?

Userspace may or may not have access to sysfs (it does not have to be
mounted) and one can have modules (input handlers) that want to bind to
a specific device (see joydev, mousedev as examples, although they are
not looking for specific keys).

> 
> What in user space looks at input devices other than X and Wayland?  And
> those aren't looking for particular "interesting" keys are they?
> 
> > I don't know why Xen keyboard exports that many keycodes ;) In general,
> > my recommendation is to mirror the physical device when possible, and
> > instantiate several devices so there is 1:1 relationship between virtual
> > and physical devices.
> 
> Xen guys: any input as to why it supports so many "interesting" keys?
> 

Thanks.

-- 
Dmitry