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 :). Thanks! -- Chase -- 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
