linux-kernel - Re: [PATCH 2/2] input: mt: Document the MT event slot protocol (rev3)

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Date:	Sat, 22 May 2010 16:52:29 -0400
From:	Chase Douglas <chase.douglas@...onical.com>
To:	Henrik Rydberg <rydberg@...omail.se>
Cc:	Rafi Rubin <rafi@...s.upenn.edu>,
	Dmitry Torokhov <dmitry.torokhov@...il.com>,
	Ping Cheng <pinglinux@...il.com>,
	Andrew Morton <akpm@...ux-foundation.org>,
	linux-input@...r.kernel.org, linux-kernel@...r.kernel.org,
	Mika Kuoppala <mika.kuoppala@...ia.com>,
	Peter Hutterer <peter.hutterer@...-t.net>,
	Benjamin Tissoires <tissoire@...a.fr>,
	Stephane Chatty <chatty@...c.fr>,
	Michael Poole <mdpoole@...ilus.org>
Subject: Re: [PATCH 2/2] input: mt: Document the MT event slot protocol
 (rev3)

On Sat, 2010-05-22 at 19:47 +0200, Henrik Rydberg wrote:
> Chase Douglas wrote:
> > On Sat, 2010-05-22 at 12:38 +0200, Henrik Rydberg wrote:
> >> Getting serious, it is anyone's guess what will happen next, but I was picturing
> >> a table, with a large multitouch screen and buttons along the side of the table.
> >> Sure, we can do "ABS_BTN_0", "ABS_BTN_1", etc, but with slots in place, it seems
> >> more natural to use something like "ABS_MT_BTN_X". While at it, REL_MT event
> >> makes sense for those touchscreen techniques which register changes, like
> >> acoustic pulse recognition.
> 
> s/ABS/KEY/
> 
> > 
> > Shouldn't this be handled in userspace? I don't think we want to be
> > quirking drivers for instances where the same touchscreen is overlaid on
> > buttons in some cases, but not in others. If we don't quirk, we'd need
> > some mechanism to tell the driver about such buttons.
> 
> Perhaps you would like to clarify what "this" means here, and how you arrive at
> quirking drivers.

I'm arriving rather late to the conversation, so this could be a matter
of me not understanding everything. What I thought you were proposing is
something like what I have on my Nexus One: an MT area encompassing a
touchscreen and extending to an area of four "buttons" off the bottom of
the screen. I was thinking that interactions with these buttons would
trigger the KEY_MT_BTN events you mentioned. However, if thats the case
then the driver needs to know of these buttons, so we've gone from a
dumb touchscreen driver to a driver that must be aware of regions of the
screen where there are buttons. This is where I think it would be better
to have a userspace application (X?) understand the properties of the
screen to know exactly what a touch means, instead of trying to
interpret it inside the kernel.

If this isn't what you meant, then feel free to ignore me :).

-- Chase

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