On Wed, Jul 06, 2011 at 07:15:07AM +0800, Daniel Kurtz wrote: > On Wed, Jul 6, 2011 at 7:06 AM, Chase Douglas > <chase.douglas@xxxxxxxxxxxxx> wrote: > > On 07/05/2011 03:50 PM, Daniel Kurtz wrote: > >> On Wed, Jul 6, 2011 at 1:42 AM, Chase Douglas > >> <chase.douglas@xxxxxxxxxxxxx> wrote: > >>> > >>> On 06/28/2011 10:07 PM, djkurtz@xxxxxxxxxxxx wrote: > >>>> From: Daniel Kurtz <djkurtz@xxxxxxxxxxxx> > >>>> > >>>> Synaptics touchpads report increasing y from bottom to top. > >>>> This is inverted from normal userspace "top of screen is 0" coordinates. > >>>> Thus, the kernel driver reports inverted y coordinates to userspace. > >>>> > >>>> In some cases, however, y = 0 is sent by the touchpad. > >>>> In these cases, the kernel driver should not invert, and just report 0. > >>> > >>> Under what cases is y sent as 0, and why do we want to report it as 0 to > >>> userspace? > >> > >> I know of two such cases for the image sensor: > >> (1) When all fingers, save the first finger are removed, an AGM > >> packet with (x=0, y=0, z=0) is sent. > >> (2) When all fingers are removed, an SGM packet with (x=0, y=0, z=0) is sent. > >> > >> After uploading this patch set, I played with the profile sensor > >> again, and I also saw it sometimes sends y=1 packets. I don't know > >> what those are. > >> > >> This is mostly useful for debugging the kernel driver. > >> When observing the raw position values, the special 0 (and 1?) cases > >> are more obvious when not inverted. > >> I think I am misleading in my commit message. I don't believe these > >> are actually ever passed through to userspace. > > > > If they are set, then they are passed through evdev, unless I'm missing > > something... Given the cases listed above, it seems like we should be > > special casing these scenarios. Maybe that means dropping the event or > > handling finger count transitions or something else. > > > > I'm happy with the patch as a cleanup of y inversion, but I don't see > > the utility of passing y = 0 through. With all the debugging techniques > > we have (printk, systemtap, perf, ftrace, etc.), I don't think we need > > this functionality, and it might lead a code reviewer to scratch their > > head wondering what the point was :). > > I meant if you were to printk y, it is much more obvious to see y=0 > than y=5321 or something like that. > I don't think this reaches userspace because y=0 packets are usually > filtered out since z and x are also 0. > > I guess this is the point, actually, that wasn't clear to me in > Henrik's astute observation: > We should do the conversion when reporting to userspace. Thus, only > do the conversion for packets that aren't already masked! > > I will refactor to an inline function, but put the conversion back in > the input_report_abs() calls. Better yet, drop this patch completely. If there is no (or low) pressure coordinate values are not interesting and shoudl be ignored by both humans and userspase consumers. Thanks. -- Dmitry -- To unsubscribe from this list: send the line "unsubscribe linux-input" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
