Re: [PATCH 2/2] elantech: Report multitouch with proper ABS_MT messages

[Henrik Rydberg <rydberg@euromail.se>]

Éric Piel wrote:
> Op 05-05-10 20:01, Henrik Rydberg schreef:
>> Dmitry Torokhov wrote:
>>>> @@ -253,7 +253,6 @@ static void elantech_report_absolute_v2(struct psmouse *psmouse)
>>>>  
>>>>  	/* byte 0: n1  n0   .   .   .   .   R   L */
>>>>  	fingers = (packet[0] & 0xc0) >> 6;
>>>> -	input_report_key(dev, BTN_TOUCH, fingers != 0);
>>> Mousedev works a tad better if BTN_TOUCH is reported first. Otherwise
>>> looks good.
>>>
>>> Henrik, should we report "tool width" as ABS_MT_WIDTH_MAJOR?
>> I might be missing some context here, I see no prior use of width in the driver.
>> The answer is either ABS_MT_TOUCH_MAJOR or ABS_MT_WIDTH_MAJOR depending on how
>> the width is actually computed. Generally, it makes little sense to have
>> ABS_MT_WIDTH_MAJOR (width of approaching finger) without ABS_MT_TOUCH_MAJOR
>> (width of touching finger), but it is ok to have only ABS_MT_TOUCH_MAJOR. Things
>> like thumb detection requires both values to be reliable.
> Ok, so it seems in this case, ABS_MT_TOUCH_MAJOR is the most
> appropriate... if we care at all.
> 
> Let me give you some more details. From what is seems, the hardware can
> reports the width of a touch, but only when there is one single touch.
> So far we report it via ABS_TOOL_WIDTH. When there is 2 or 3 touches,
> the width is unknown. So the precise question is:
> Should we report also ABS_MT_TOUCH_MAJOR in addition to ABS_TOOL_WIDTH,
> whenever it is known (ie: one finger), or just not bother and only
> report ABS_TOOL_WIDTH?

With only partial information available it will not be of much use anyway, so
omitting ABS_MT_TOUCH is probably best. The ABS_TOOL_WIDTH will most likely not
be used by a driver either (it wont in the Multitouch X Driver anyways). The
synaptics driver cares for palm detection, but the scale has to be very specific
to work properly (i.e., requires testing with synaptics to be useful).

Henrik

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