Re: [PATCH] Input: Support for a less exclusive grab.

Zephaniah E. Hull
2007-06-12T05:23:31Z

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*googles briefly for rfkill-input, looks for his brown paper bag*

On Tue, Jun 12, 2007 at 01:19:59AM -0400, Dmitry Torokhov wrote:
> On Tuesday 12 June 2007 01:12, Zephaniah E. Hull wrote:
> > On Tue, Jun 12, 2007 at 01:07:13AM -0400, Dmitry Torokhov wrote:
> > > Hi Zephaniah,
> > >
> > > On Saturday 09 June 2007 04:48, Zephaniah E. Hull wrote:
> > > > EVIOCGRAB is nice and very useful, however over time I've gotten
> > > > multiple requests to make it possible for applications to get events
> > > > straight from the event device while xf86-input-evdev is getting events
> > > > from the same device.
> > > >
> > > > Here is the least invasive patch I could think of, it changes the
> > > > behavior of EVIOCGRAB in some cases, specificly behavior is identical if
> > > > the argument is 0 or 1, however if the argument is true and != 1, then
> > > > it does a 'non exclusive grab', a better name might be handy.
> > > >
> > > > What this does is allow the events to go to everything that's using
> > > > evdev to get events, but grabs it from anything else.  About as close to
> > > > what people want as I can get, and fairly non-invasive.
> > >
> > > Unfortunately this also robs non-legacy input handlers (such as
> > > rfkill-input) of input events. Does xf86-input-evdev really needs to
> > > grab devices exclusively? I guess we can't abandon the standard
> > > keyboard driver until X supports hotplugging. How close is it to
> > > support devices coming and going?
> >
> > Er, to explain.
> >
> > The current EVIOCGRAB does an exclusive grab that prohibits rfkill-input
> > and friends from working.
> >
>
> I understand that.
>
> > As it is the only way to disable the legacy input handlers,
> > xf86-input-evdev has been using it since we added it.
> >
>
> Like I said I would love if xf86-input-evdev did not grab the
> device at all.

We have to disable the legacy input handlers somehow, not doing so
simply isn't an option.
>
> > The patch is to let us cause only things that use /dev/input/event<n> to
> > get events, thus, a non-exclusive grab.
> >
> > This basicly disables the legacy input handlers, and it's the least
> > invasive patch I could think of.
> >
>
> But rfkill-input is not a legacy handler. My objection is that with your
> solution you still will rob handlers such rfkill-input of events.

Urgh.

So, any thoughts on how to identify legacy input handlers in the input
system?

This is a tricky case I had not even been aware of.
>
> > Going for a separate ioctl would also work, but in some ways it would
> > make supporting it more of a pain.
> >
> > I don't care _that_ much either way, as long as we can get a way to
> > disable the legacy events while allowing other things to get the events
> > too.
> >
> > Zephaniah E. Hull.
> > >
> > > If we can't remain as is until X hotplug is ready then I'd rather had
> > > a separate ioctl that disables legacy input handlers (keyboard, mousedev)
> > > for a given input device.
> > >
> > > --
> > > Dmitry
> > >
> >
>
> --
> Dmitry
>

--
1024D/E65A7801 Zephaniah E. Hull <warp@aehallh.com>
92ED 94E4 B1E6 3624 226D 5727 4453 008B E65A 7801
CCs of replies from mailing lists are requested.

>> kinds of numbers the tobacco industry wishes it had, and Dell is very
>> very happy with the results.
>
>Do they come with a Surgeon General warning on the box?

The new ones have "Designed for Windows XP". Yes.
-- Satya, Paul Martin, and Derek Balling in the Scary Devil Monastery.

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