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

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Message-ID: <20070612051210.GW6362@aehallh.com>
Date:	Tue, 12 Jun 2007 01:12:10 -0400
From:	"Zephaniah E. Hull" <warp@...allh.com>
To:	Dmitry Torokhov <dtor@...ightbb.com>
Cc:	linux-input@...ey.karlin.mff.cuni.cz, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] Input: Support for a less exclusive grab.

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.

As it is the only way to disable the legacy input handlers,
xf86-input-evdev has been using it since we added it.

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.

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
> 

-- 
	  1024D/E65A7801 Zephaniah E. Hull <warp@...allh.com>
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