linux-kernel - Re: [PATCH] input: Add a detailed multi-touch finger data report protocol

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Date:	Fri, 21 Nov 2008 15:44:44 +0100
From:	Henrik Rydberg <rydberg@...math.org>
To:	Dmitry Torokhov <dmitry.torokhov@...il.com>
CC:	Henrik Rydberg <rydberg@...omail.se>,
	Andrew Morton <akpm@...ux-foundation.org>,
	linux-input@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] input: Add a detailed multi-touch finger data report
 protocol

Dmitry,

My patch is all wrong. It would certainly benefit from using the
EV_SYN/SYN_MT_REPORT, but the defuzz mechanism of the EV_ABS class
simply will not work when sending data for several different fingers
using the same event.

I can see two clear alternatives: either add a new event class, EV_MT,
which sends all data without trying to limit the bandwidth, or forget
about the whole serial-finger-data idea and expand the current EV_ABS
class with an array of MT finger data [1]. I would very much appreciate
your input on this. Maybe there is a third option.

Cheers,
Henrik

[1] An example of a straight-forward addition of EV_ABS/ABS_MT events:

#define ABS_MT_FINGER_CNT	10
#define ABS_MT_PROPERTY_CNT	12

#define ABS_MT_FINGER_START	0x30
#define ABS_MT_TOUCH(x)		(ABS_MT_FINGER_START + 0 * ABS_MT_FINGER_CNT + x)
#define ABS_MT_WIDTH(x)		(ABS_MT_FINGER_START + 1 * ABS_MT_FINGER_CNT + x)
...
#define ABS_MT_FINGER_END	0xa8 /* = ABS_MT_FINGER_START + ABS_MT_PROPERTY_CNT * ABS_MT_FINGER_CNT */

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