HID: input: simplify/fix high-res scroll event handling
[muen/linux.git] / drivers / hid / hid-input.c
index 567c3bf64515d3599946c1d74aa79d52d9a61620..a2f74e6adc70d162adf641ac3f02ae452e3552a3 100644 (file)
@@ -1855,31 +1855,30 @@ EXPORT_SYMBOL_GPL(hidinput_disconnect);
 void hid_scroll_counter_handle_scroll(struct hid_scroll_counter *counter,
                                      int hi_res_value)
 {
-       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;
+       int low_res_value, remainder, multiplier;
 
        input_report_rel(counter->dev, REL_WHEEL_HI_RES,
                         hi_res_value * counter->microns_per_hi_res_unit);
 
-       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;
-       }
+       /*
+        * 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);
 }
 EXPORT_SYMBOL_GPL(hid_scroll_counter_handle_scroll);