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

From: Chase Douglas
Date: Sat May 22 2010 - 16:52:53 EST

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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