On Fri, Feb 01, 2013 at 04:28:32PM +0800, Daniel Kurtz wrote: > The input fuzz algorithm does a pretty good job filtering out small > jitter on input samples. > > However, there is a subtle problem when fuzz is used with mt drivers that > also use input_mt_report_pointer_emulation() to report legacy single > touch coordinates. The reported single touch coordinates are taken from > the active MT slot with smallest tracking id. However, since the MT data > is sent first, it has already had FUZZ applied. Thus, the ST coordinates > actually get FUZZ applied a second time, with the just-fuzzed MT value as > the 'old value'. > > It appears that it is non-trivial to fix this in the mt layer/input core, > so, for now, just disable fuzz for the synaptics IMAGE_SENSOR path that > uses input_mt_report_pointer_emulation(). > > Signed-off-by: Daniel Kurtz <djku...@chromium.org> > --- > drivers/input/mouse/synaptics.c | 3 ++- > 1 file changed, 2 insertions(+), 1 deletion(-) > > diff --git a/drivers/input/mouse/synaptics.c b/drivers/input/mouse/synaptics.c > index 12d12ca..b6c6838 100644 > --- a/drivers/input/mouse/synaptics.c > +++ b/drivers/input/mouse/synaptics.c > @@ -1211,7 +1211,8 @@ static void set_abs_position_params(struct input_dev > *dev, > int x_max = priv->x_max ?: XMAX_NOMINAL; > int y_min = priv->y_min ?: YMIN_NOMINAL; > int y_max = priv->y_max ?: YMAX_NOMINAL; > - int fuzz = SYN_CAP_REDUCED_FILTERING(priv->ext_cap_0c) ? > + int fuzz = (SYN_CAP_REDUCED_FILTERING(priv->ext_cap_0c) && > + !SYN_CAP_IMAGE_SENSOR(priv->ext_cap_0c)) ? > SYN_REDUCED_FILTER_FUZZ : 0;
Hmm, instead of disabling fuzz completely maybe we should disable it only on the derived axes (ABS_X/ABS_Y) for multitouch devices? Thanks. -- Dmitry -- To unsubscribe from this list: send the line "unsubscribe linux-input" in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
