linux-kernel - Re: [PATCH 2/3] Input: synaptics - add multi-finger and semi-mt support

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Date:	Tue, 21 Dec 2010 12:06:08 -0600
From:	Chris Bagwell <chris@...bagwell.com>
To:	Henrik Rydberg <rydberg@...omail.se>
Cc:	Chase Douglas <chase.douglas@...onical.com>,
	Dmitry Torokhov <dmitry.torokhov@...il.com>,
	Jiri Kosina <jkosina@...e.cz>, Takashi Iwai <tiwai@...e.de>,
	linux-input@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH 2/3] Input: synaptics - add multi-finger and semi-mt support

On Tue, Dec 21, 2010 at 10:59 AM, Henrik Rydberg <rydberg@...omail.se> wrote:
>> > Reported-by: Tobyn Bertram
>> > Not-yet-signed-off-by: Takashi Iwai <tiwai@...e.de>
>> > Not-yet-signed-off-by: Chase Douglas <chase.douglas@...onical.com>
>> > Not-yet-signed-off-by: Chris Bagwell <chris@...bagwell.com>
>> > Signed-off-by: Henrik Rydberg <rydberg@...omail.se>
>>
>> You can keep my SOB.
>
> Great, thanks.
>
>> > +static void set_slot(struct input_dev *dev, int slot, bool active, int x, int y)
>> > +{
>> > +   input_mt_slot(dev, slot);
>> > +   input_mt_report_slot_state(dev, MT_TOOL_FINGER, active);
>> > +   if (active) {
>> > +           input_report_abs(dev, ABS_MT_POSITION_X, x);
>> > +           input_report_abs(dev, ABS_MT_POSITION_Y,
>> > +                            YMAX_NOMINAL + YMIN_NOMINAL - y);
>> > +   }
>> > +}
>>
>> I take it that you feel MT_TOOL_FINGER should always be set, even if
>> it's always the same as BTN_TOOL_*? I just want to be sure this is
>> intended so we document it appropriately.
>
> Yes - the MT_TOOLs are only emitted when explicitly set in absbit, but
> the internal interface always handles it. This is actually documented
> in the code (and DocBook).

That note is good guidance for developer side.  Its also worth noting
on app side that MT_TOOL_FINGER is a little special since its value is
0.  In most common case, I think it will get filtered out where as
BTN_TOOL_FINGER will always be sent.

Since we can't yet query per slot ABS_MT_TOOL_TYPE, I guess apps have
to just assume its a finger unless told otherwise?

Chris
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