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evdev: Implement fuzz.

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Fuzz is used to filter noise from the event stream.
Upcoming gamepad drivers use it.

Reviewed by:	hselasky (as part of D27993)
This commit is contained in:
Vladimir Kondratyev 2020-12-01 00:10:04 +03:00
parent 9be6b22da9
commit 3b2175fdb6
1 changed files with 19 additions and 1 deletions
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20
sys/dev/evdev/evdev.c
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@ -684,6 +684,7 @@ static void
evdev_modify_event(struct evdev_dev *evdev, uint16_t type, uint16_t code,
int32_t *value)
{
int32_t fuzz, old_value, abs_change;
EVDEV_LOCK_ASSERT(evdev);
@ -710,7 +711,24 @@ evdev_modify_event(struct evdev_dev *evdev, uint16_t type, uint16_t code,
break;
case EV_ABS:
/* TBD: implement fuzz */
fuzz = evdev->ev_absinfo[code].fuzz;
if (fuzz == 0 || code == ABS_MT_SLOT)
break;
else if (!ABS_IS_MT(code))
old_value = evdev->ev_absinfo[code].value;
else if (bit_test(evdev->ev_abs_flags, ABS_MT_SLOT))
old_value = evdev_get_mt_value(evdev,
evdev_get_last_mt_slot(evdev), code);
else /* Pass MT protocol type A events as is */
break;
abs_change = abs(*value - old_value);
if (abs_change < fuzz / 2)
*value = old_value;
else if (abs_change < fuzz)
*value = (old_value * 3 + *value) / 4;
else if (abs_change < fuzz * 2)
*value = (old_value + *value) / 2;
break;
}
}