On Wed, Jul 25, 2012 at 3:31 AM, Seth Forshee <seth.forshee@xxxxxxxxxxxxx> wrote: > The touchpad on the Acer Aspire One D250 will report out of range values > in the extreme lower portion of the touchpad. These appear as abrupt > changes in the values reported by the hardware from very low values to > very high values, which can cause unexpected vertical jumps in the > position of the mouse pointer. > > What seems to be happening is that the value is wrapping to a two's > compliment negative value of higher resolution than the 13-bit value > reported by the hardware, with the high-order bits being truncated. This > patch adds handling for these values by converting them to the > appropriate negative values. > > The only tricky part about this is deciding when to treat a number as > negative. It stands to reason that if out of range values can be > reported on the low end then it could also happen on the high end, so > not all out of range values should be treated as negative. The approach > taken here is to split the difference between the maximum legitimate > value for the axis and the maximum possible value that the hardware can > report, treating values greater than this number as negative and all > other values as positive. This can be tweaked later if hardware is found > that operates outside of these parameters. > > BugLink: http://bugs.launchpad.net/bugs/1001251 > Cc: stable@xxxxxxxxxxxxxxx > Cc: Daniel Kurtz <djkurtz@xxxxxxxxxxxx> > Signed-off-by: Seth Forshee <seth.forshee@xxxxxxxxxxxxx> > --- > drivers/input/mouse/synaptics.c | 22 ++++++++++++++++++++++ > 1 file changed, 22 insertions(+) > > diff --git a/drivers/input/mouse/synaptics.c b/drivers/input/mouse/synaptics.c > index c6d9869..ce345c5 100644 > --- a/drivers/input/mouse/synaptics.c > +++ b/drivers/input/mouse/synaptics.c > @@ -40,11 +40,27 @@ > * Note that newer firmware allows querying device for maximum useable > * coordinates. > */ > +#define XMIN 0 > +#define XMAX 6143 > +#define YMIN 0 > +#define YMAX 6143 > #define XMIN_NOMINAL 1472 > #define XMAX_NOMINAL 5472 > #define YMIN_NOMINAL 1408 > #define YMAX_NOMINAL 4448 > > +/* Size in bits of absolute position values reported by the hardware */ > +#define ABS_POS_BITS 13 > + > +/* > + * Any position values from the hardware above the following limits are > + * treated as "wrapped around negative" values that have been truncated to > + * the 13-bit reporting range of the hardware. These are just reasonable > + * guesses and can be adjusted if hardware is found that operates outside > + * of these parameters. > + */ > +#define X_MAX_POSITIVE (((1 << ABS_POS_BITS) + XMAX) / 2) > +#define Y_MAX_POSITIVE (((1 << ABS_POS_BITS) + YMAX) / 2) > > /***************************************************************************** > * Stuff we need even when we do not want native Synaptics support > @@ -555,6 +571,12 @@ static int synaptics_parse_hw_state(const unsigned char buf[], > hw->right = (buf[0] & 0x02) ? 1 : 0; > } > > + /* Convert wrap-around values to negative */ > + if (hw->x > X_MAX_POSITIVE) > + hw->x = hw->x - (1 << ABS_POS_BITS); Hi Seth, Perhaps: hw->x -= (1 << ABS_POS_BITS); Either way, it looks good, thanks! Reviewed-by: Daniel Kurtz <djkurtz@xxxxxxxxxxxx> > + if (hw->y > Y_MAX_POSITIVE) > + hw->y = hw->y - (1 << ABS_POS_BITS); > + > return 0; > } > > -- > 1.7.9.5 -- 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
