1 files changed, 22 insertions, 21 deletions

diff --git a/drivers/hid/hid-input.c b/drivers/hid/hid-input.c
index 44ea8e7c71a9..28ee2ed88a1a 100644
--- a/drivers/hid/hid-input.c
+++ b/drivers/hid/hid-input.c
@@ -1858,30 +1858,31 @@ EXPORT_SYMBOL_GPL(hidinput_disconnect);
 void hid_scroll_counter_handle_scroll(struct hid_scroll_counter *counter,
                                       int hi_res_value)
 {
-        int low_res_value, remainder, multiplier;
+        int low_res_scroll_amount;
+        /* Some wheels will rest 7/8ths of a notch from the previous notch
+         * after slow movement, so we want the threshold for low-res events to
+         * be in the middle of the notches (e.g. after 4/8ths) as opposed to on
+         * the notches themselves (8/8ths).
+         */
+        int threshold = counter->resolution_multiplier / 2;
 
         input_report_rel(counter->dev, REL_WHEEL_HI_RES,
                          hi_res_value * counter->microns_per_hi_res_unit);
 
-        /*
-         * Update the low-res remainder with the high-res value,
-         * but reset if the direction has changed.
-         */
-        remainder = counter->remainder;
-        if ((remainder ^ hi_res_value) < 0)
-                remainder = 0;
-        remainder += hi_res_value;
-
-        /*
-         * Then just use the resolution multiplier to see if
-         * we should send a low-res (aka regular wheel) event.
-         */
-        multiplier = counter->resolution_multiplier;
-        low_res_value = remainder / multiplier;
-        remainder -= low_res_value * multiplier;
-        counter->remainder = remainder;
-
-        if (low_res_value)
-                input_report_rel(counter->dev, REL_WHEEL, low_res_value);
+        counter->remainder += hi_res_value;
+        if (abs(counter->remainder) >= threshold) {
+                /* Add (or subtract) 1 because we want to trigger when the wheel
+                 * is half-way to the next notch (i.e. scroll 1 notch after a
+                 * 1/2 notch movement, 2 notches after a 1 1/2 notch movement,
+                 * etc.).
+                 */
+                low_res_scroll_amount =
+                        counter->remainder / counter->resolution_multiplier
+                        + (hi_res_value > 0 ? 1 : -1);
+                input_report_rel(counter->dev, REL_WHEEL,
+                                 low_res_scroll_amount);
+                counter->remainder -=
+                        low_res_scroll_amount * counter->resolution_multiplier;
+        }
 }
 EXPORT_SYMBOL_GPL(hid_scroll_counter_handle_scroll);