Re: [PATCH v2 1/3] hid-multitouch: add support for trackpads

[Dmitry Torokhov <dmitry.torokhov@gmail.com>]

On Fri, Jan 20, 2012 at 05:09:48PM +0100, Henrik Rydberg wrote:
> Hi Benjamin,
> 
> > @@ -389,9 +404,19 @@ static int mt_input_mapping(struct hid_device *hdev, struct hid_input *hi,
> >  				td->last_field_index = field->index;
> >  			return -1;
> >  		}
> > +		case HID_DG_TOUCH:
> > +			/* Legacy devices use TIPSWITCH and not TOUCH.
> > +			 * Let's just ignore this field. */
> > +			return -1;
> >  		/* let hid-input decide for the others */
> >  		return 0;
> >  
> > +	case HID_UP_BUTTON:
> > +		code = ((usage->hid - 1) & HID_USAGE) + BTN_MOUSE;
> 
> Why '+' here instead of '|' is  beyond me...

Because it is an offset for the range. The fact that it is on power 2
boundary and we can use "|" is purely coincidential here.

Maybe we should even write it as:

		code = BTN_MOUSE + ((usage->hid - 1) & HID_USAGE);

Thanks,
Dmitry

-- 
Dmitry