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

From: Henrik Rydberg
Date: Sat May 22 2010 - 06:39:38 EST

Rafi Rubin wrote:
> On 05/21/10 13:49, Henrik Rydberg wrote:
>> Dmitry Torokhov wrote:
>>> I guess this is where our disconnect lies as when I am looking at the
>>> event names I view all *_MT_* events as related to the multitouch
>>> protocol handling.
>> Yes. It is true that slot control is MT related, but I am looking at this from
>> the perspective of future expansions like KEY_MT, KEY_REL, and such, finding a
>> way to signal to user space which events are handled via slots. If we had
>> ABS_MT_SLOT, we would most likely get applications which store ABS_MT_SLOT as an
>> attribute of the slot together with ABS_MT_POSITION_X, ABS_MT_TOUCH_MAJOR, etc,
>> which is just not right. So the proposal is ABS_SLOT. May we have your verdict,
>> please. :-)
>> Henrik
> How many fingers can type on cap of a key?

It depends on the size of the key, does it not. :-)

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.

> Seems to me like part of the problem here is still the overlap between tracking
> id and slot id.

Would you care to elaborate?


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