Re: [PATCH 3/4] input/alps: Allow touchsticks to report pressure

[Ben Gamari <ben@smart-cactus.org>]

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Hans de Goede <hdegoede@redhat.com> writes:

> Hi,
>>
>> @@ -2996,6 +2999,10 @@ int alps_init(struct psmouse *psmouse)
>>
>>  		input_set_capability(dev2, EV_REL, REL_X);
>>  		input_set_capability(dev2, EV_REL, REL_Y);
>> +		if (priv->flags & ALPS_DUALPOINT_WITH_PRESSURE) {
>> +			input_set_capability(dev2, EV_ABS, ABS_PRESSURE);
>> +			input_set_abs_params(dev2, ABS_PRESSURE, 0, 127, 0, 0);
>> +		}
>>  		input_set_capability(dev2, EV_KEY, BTN_LEFT);
>>  		input_set_capability(dev2, EV_KEY, BTN_RIGHT);
>>  		input_set_capability(dev2, EV_KEY, BTN_MIDDLE);
>
> This seems wrong, reporting ABS_PRESSURE on a relative device. And yes, this
> really is a relative device (it sends repeated delta events when you
> keep pushing at the same force, rather then sending a single coordinate
> value).
>
> Maybe we need a REL_PRESSURE for cases like this ?
>
Fair enough. However, if such a thing were added how would one specify
the range of the value (which seems necessary for the pressure to have
any meaning whatsoever)? It seems odd that the distinctions of
absolute/relative and bounded/unbounded values are conflated in the
event interface. It's not clear to me what input_set_abs_params isn't
instead input_set_params.

Cheers

- Ben

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