Warning: evdev changes - no auto-grabs anymore

Adam Jackson ajax at nwnk.net
Thu Aug 14 10:50:09 PDT 2008

On Thu, 2008-08-14 at 16:54 +0200, Michel Dänzer wrote:
> On Thu, 2008-08-14 at 14:13 +0930, Peter Hutterer wrote:
> > Just a warning to all evdev users. I just pushed a fix to disable device grabs
> > by default to evdev git (not X active/passive grabs, EVIOCGRAB ones).
> > 
> > Why? 
> > If you grab a device, you will stop it from sending events to /dev/input/mice,
> > /dev/kbd, but breaks other (virtual) devices such as the Macintosh mouse
> > button emulation and rfkill.
> Sounds good, but unfortunately, this change seems to cause trouble of
> its own, namely that hitting ctrl-C terminates the X server - not very
> useful. :) It looks like all the input intended for the X server also
> goes to a VT (I can briefly see fragments of what I typed before hitting
> ctrl-C until the server restarts), and that's probably how the ctrl-C
> results in a SIGTERM to the X server.

This is, in fact, one of the main reasons I put SIOCGRAB there in the
first place; you need to keep the keyboard's event stream out of the tty
layer entirely, not just out of reach of the kbd driver.  At the time
the argument was also that you wanted to keep them out of reach of
normal users so you couldn't snoop passwords, but now that there's a
ConsoleKit I think that's less true.

Mac mouse emulation we could probably just blacklist away from the evdev
driver.  rfkill is... harder?  Does it get its own event device or not?
I'd think it would have to get one kill device per wireless device.

- ajax
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