On Mon, Jan 24, 2011 at 10:36 AM, Dmitry Torokhov
<dmitry.torokhov@xxxxxxxxx> wrote:
> On Mon, Jan 24, 2011 at 10:18:54AM -0800, Ping Cheng wrote:
>> On Mon, Jan 24, 2011 at 6:40 AM, Henrik Rydberg <rydberg@xxxxxxxxxxx> wrote:
>> > Hi Ping,
>> >
>> >> @@ -1228,8 +1228,13 @@ void wacom_setup_input_capabilities(struct input_dev *input_dev,
>> >> case TABLETPC:
>> >> if (features->device_type == BTN_TOOL_DOUBLETAP ||
>> >> features->device_type == BTN_TOOL_TRIPLETAP) {
>> >> - input_set_abs_params(input_dev, ABS_RX, 0, features->x_phy, 0, 0);
>> >> - input_set_abs_params(input_dev, ABS_RY, 0, features->y_phy, 0, 0);
>> >> + /* set touch resolution in points/mm */
>> >> + res = features->x_phy/100;
>> >> + input_abs_set_res(input_dev, ABS_X,
>> >> + features->x_max/res);
>> >
>> > It seems to me the construction above looses precision twice for no
>> > apparent reason.
>>
>> Well, there was a reason (logically instead of mathematically though):
>> features->x_phy/100 gives us the physical size of the touch area in
>> mm.
>>
>> > How about instead use "100 * features->x_max /
>> > features->x_phy"?
>>
>> Sure.
>>
>> > Besides, it is a bit unfortunate that "res" is short
>> > for both result and resolution.
>>
>> Resolution is defined as __s32 in input_absinfo. How about we use __s32 then?
>
> input_abs_set_res() takes and int argument so keep it int (or just
> embed the expression into the call and forgo 'res').
I added 'res' to avoid confusion hence questions about the formula. I
am still questioned ;).
I'll forgo 'res' in v2. Thank you for the suggestions.
Ping
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