linux-kernel - Re: [PATCH 0/4] Alternative approach to MT_TOOL

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Message-ID: <4D081BF2.7000202@euromail.se>
Date:	Wed, 15 Dec 2010 02:37:54 +0100
From:	Henrik Rydberg <rydberg@...omail.se>
To:	Chase Douglas <chase.douglas@...onical.com>
CC:	Dmitry Torokhov <dmitry.torokhov@...il.com>,
	Chris Bagwell <chris@...bagwell.com>,
	Peter Hutterer <peter.hutterer@...-t.net>,
	linux-input@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH 0/4] Alternative approach to MT_TOOL_ENVELOPE

Hi Chase,

>

> I gave this some more thought, and I was close to accepting it with
> documentation of the above restrictions. Then I thought of how the
> following two devices would be presented to userspace:
> 
> 1. A real MT device supporting up to 2 touches (e.g. a bamboo touch)
>   - ABS_{X,Y}, BTN_TOUCH, BTN_TOOL_FINGER, and BTN_TOOL_DOUBLETAP for ST
>   - ABS_MT_SLOT, ABS_MT_TRACKING_ID, ABS_MT_POSITION_{X,Y}, ABS_MT_TOOL_TYPE
> 
> 2. A partial MT device using MT_TOOL_ENVELOPE (e.g. synaptics MT)
>   - ABS_{X,Y}, BTN_TOUCH, BTN_TOOL_FINGER, and BTN_TOOL_DOUBLETAP for ST
>   - ABS_MT_SLOT, ABS_MT_TRACKING_ID, ABS_MT_POSITION_{X,Y}, ABS_MT_TOOL_TYPE
> 
> Note that they are identical! The range of values for each axis would be
> identical too. The only way to tell the two apart would be to watch for
> the ABS_MT_TOOL_TYPE axis.


Ping has touched upon this subject as well, from the pen & touch perspective.
Generally, some ABS axes are actually enumerations, for which we have no direct
abstraction. If we had a way to declare the used values for such enumerations,
it would resolve these and possibly other issues.

Thanks,
Henrik

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