Re: event mixer patch

[Vojtech P. <vo...@su...>]

On Tue, Jun 19, 2001 at 03:48:01PM -0700, James Simmons wrote:
> 
> > > Is this a seperate patch or the patch from Charles? I looked at his patch
> > > and it has only one line change in input.c. Very nice patch. After I'm
> > > done with power management today I will incorporate it. Probable some
> > > time tomorrow unless Vojtech has any objections.
> > 
> > Last time I asked Vojtech wasn't very pleased of that idea, eg. it doesn't 
> > make  much sense to mix in EV_ABS devices.
> 
> Your right. I have this problem with a userland program I wrote. The way
> I got around that was to emulate each absolute device as a relative
> device. 
> 
> > Maybe it should be a separate module providing a whole class of event mix 
> > devices, with all EV_KEY and EV_REL mixed on /dev/eventmix0 by default. Then 
> > there could be ioctl's to attach and detach single event devices onto the 
> > mixer devices.
> 
> The real underlying problem is knowing when a device gets attached and
> detached. 

USB currently handles this with a select() on /proc/bus/usb/devices. I
think we could do the same. Actually a /proc/..../input/devices file
would be quite useful.

As for detaching, evdev now returns -ENODEV on read() when a device is
detached.

> How do we know that? It is not easy to solve. A mixer sort of
> gets around this problem. Then we run into the problem of EV_ABS type
> devices. The mixer device could be used to tell us when a new device is
> added or subtracted. Then we can decided to add the new device to the
> mixer. 

-- 
Vojtech Pavlik
SuSE Labs