On Wed, Feb 13, 2013 at 1:52 PM, Dmitry Torokhov <dmitry.torokhov@xxxxxxxxx> wrote: > 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 <djkurtz@xxxxxxxxxxxx> >> --- >> 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? Yes, that should work... both would end up fuzzed to the same value, for a not-so-obvious reason, IMHO :). It's a bit tricky, and I like it, but is that what you intended by the suggestion? -Daniel > > 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
