On Sun, 25 Mar 2007 01:34:02 -0400, Dmitry Torokhov <[EMAIL PROTECTED]> wrote:
> > + * Without this, a touchpad may report an unchanged > > position, > > + * then a sync. The input_event() eats the position report, > > but > > + * lets the sync through. We increment pkt_count and leave > > + * a stale position in the ring. If a future reference to > > fx(2) > > + * hits the stale position, a large dx is reported, and the > > + * pointer warps across the screen. > > + */ > > + dev = mousedev->handle.dev; > > + fx(0) = dev->abs[ABS_X]; > > + fy(0) = dev->abs[ABS_Y]; > > I do not like input hanlders poking into input devices... Can't we just > reset pkt_count at the beginning of the touch to get rid of stale data? The pkt_count is zero at the moment of assignment above. Please look at the included trace again: > > Event: time 1174703243.305535, type 1 (Key), code 330 (Touch), value 1 > > <---- touch!=0 now, we're on > > Event: time 1174703243.305538, type 3 (Absolute), code 24 (Pressure), value > > 31 > > Event: time 1174703243.305541, -------------- Report Sync ------------ > > <---- We increment the pkt_count, leaving value of 3687 in old_y > > Event: time 1174703243.342452, type 3 (Absolute), code 0 (X), value 4747 > > Event: time 1174703243.342455, type 3 (Absolute), code 1 (Y), value 1988 > > <----- Later to be fy(1), not used for warping purposes :-) > > Event: time 1174703243.342459, -------------- Report Sync ------------ > > Event: time 1174703243.356225, type 3 (Absolute), code 0 (X), value 4749 > > Event: time 1174703243.356237, type 3 (Absolute), code 1 (Y), value 1987 > > <----- warp here, by the difference of 3687 and 1987, plus > > some small frac_dy value. Easily jumps half the screen. > > Event: time 1174703243.356246, -------------- Report Sync ------------ The assignment happens at .305535. The pkt_count is zero, and fy(0) contains stale data (ovewritten by the assignment). The touchpad reports a position next with input_report_abs(). If the position were different, we'd receive an event between .305535 and .305538 and it would be stored in fy(0). However, if position is the same, as in this case, input_report eats it. At .305541 we increment pkt_count. The fy(0) location becomes fy(1) at this point. Without the assignment it contains the stale position. I can explore alternatives, but for now using dev->abs[] seems to be most expedient. -- Pete - To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to [EMAIL PROTECTED] More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
