Re: [PATCH v3] Documentation: Add evdev type and code definitions

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

On Fri, Mar 25, 2011 at 04:04:34PM +1000, Peter Hutterer wrote:
> On Thu, Mar 24, 2011 at 10:50:23PM -0700, Dmitry Torokhov wrote:
> > On Fri, Mar 25, 2011 at 10:36:02AM +1000, Peter Hutterer wrote:
> > > On Thu, Mar 24, 2011 at 03:45:51PM -0400, Chase Douglas wrote:
> > > > On 03/24/2011 02:44 PM, Chris Bagwell wrote:
> > > > > Looking good.  Minor comments at end.
> > > > > 
> > > > > On Thu, Mar 24, 2011 at 12:44 PM, Chase Douglas
> > > > > <chase.douglas@canonical.com> wrote:
> > > > >> +Touchscreens:
> > > > >> +----------
> > > > >> +ABS_{X,Y} must be reported with the location of the touch. BTN_TOUCH must be
> > > > >> +used to report when a touch is active on the screen.
> > > > >> +BTN_{MOUSE,LEFT,MIDDLE,RIGHT} must not be reported. BTN_TOOL_<name> events
> > > > >> +should be reported where possible.
> > > > > 
> > > > > Does the real button event restriction solve something?  I know
> > > > > majority of touchscreens are not sending a button today but usually
> > > > > there is a button on the touchscreen frame that I'd image at least
> > > > > some devices hooking it up to touchscreen interface.
> > > > >
> > > > > stylus+touchscreen combo devices are surely going to want to do this.
> > > > 
> > > > Perhaps this should be more clearly for touchscreen-only devices (not
> > > > tablets or a mix). The problem we end up seeing is drivers who use
> > > > BTN_LEFT because they want a touch to generate a primary button press in
> > > > X. I want to prevent people from doing this.
> > > 
> > > suggest that they use BTN_0 instead then?
> > > 
> > 
> > Umm, I'd hope X evdev driver could handle BTN_TOUCH without
> > BTN_LEFT/BTN_0 to indicate primary button. Legacy mode (mousedev)
> > already translateds BTN_TOUCH/BTN_LEFT/BTN_0 into "left PS/2 button".
> 
> evdev treats BTN_TOUCH as button, yes. my comment above refers to additional
> buttons on the tablet that aren't touch. maybe I misread the above though.
> 

I guess it depends on the purpose of the buttons. BTN_LEFT is really a
"primary button" so would not make sense for additional buttons on a
touchscreen. BTN_0 is more like "we have no idea what it is so here you
go" though...

Thanks.

-- 
Dmitry