Merge branch 'for-4.20/logitech-highres' into for-linus
[muen/linux.git] / drivers / hid / hid-input.c
index ad823a01bd6570cd55efcea62b4e346d99949065..567c3bf64515d3599946c1d74aa79d52d9a61620 100644 (file)
@@ -1838,3 +1838,48 @@ void hidinput_disconnect(struct hid_device *hid)
 }
 EXPORT_SYMBOL_GPL(hidinput_disconnect);
 
+/**
+ * hid_scroll_counter_handle_scroll() - Send high- and low-resolution scroll
+ *                                      events given a high-resolution wheel
+ *                                      movement.
+ * @counter: a hid_scroll_counter struct describing the wheel.
+ * @hi_res_value: the movement of the wheel, in the mouse's high-resolution
+ *                units.
+ *
+ * Given a high-resolution movement, this function converts the movement into
+ * microns and emits high-resolution scroll events for the input device. It also
+ * uses the multiplier from &struct hid_scroll_counter to emit low-resolution
+ * scroll events when appropriate for backwards-compatibility with userspace
+ * input libraries.
+ */
+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;
+
+       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;
+       }
+}
+EXPORT_SYMBOL_GPL(hid_scroll_counter_handle_scroll);