HID: magicmouse: enable high-resolution scroll

The Magic Mouse, generations 1 and 2, doesn't have a physical scroll
wheel, instead, the REL_WHEEL and REL_HWHEEL events are emulated
when sliding a finger on the surface of the mouse.
However, the smooth movement of the finger is transformed into a step
based scroll on the screen, leading to a suboptimal user experience.

Emulate high-resolution scroll by sending REL_WHEEL_HI_RES and
REL_HWHEEL_HI_RES events so the scroll on the screen is closer to the
finger movement.

Signed-off-by: José Expósito <jose.exposito89@gmail.com>
Signed-off-by: Jiri Kosina <jkosina@suse.cz>

diff --git a/drivers/hid/hid-magicmouse.c b/drivers/hid/hid-magicmouse.c
index 8bcaee4..e95f46d 100644 (file)
--- a/drivers/hid/hid-magicmouse.c
+++ b/drivers/hid/hid-magicmouse.c
@@ -68,6 +68,9 @@ MODULE_PARM_DESC(report_undeciphered, "Report undeciphered multi-touch state fie
 #define TOUCH_STATE_START 0x30
 #define TOUCH_STATE_DRAG  0x40
 
+/* Number of high-resolution events for each low-resolution detent. */
+#define SCROLL_HR_STEPS 10
+#define SCROLL_HR_MULT (120 / SCROLL_HR_STEPS)
 #define SCROLL_ACCEL_DEFAULT 7
 
 /* Touch surface information. Dimension is in hundredths of a mm, min and max
@@ -126,6 +129,8 @@ struct magicmouse_sc {
                short y;
                short scroll_x;
                short scroll_y;
+               short scroll_x_hr;
+               short scroll_y_hr;
                u8 size;
        } touches[16];
        int tracking_ids[16];
@@ -248,12 +253,18 @@ static void magicmouse_emit_touch(struct magicmouse_sc *msc, int raw_id, u8 *tda
                unsigned long now = jiffies;
                int step_x = msc->touches[id].scroll_x - x;
                int step_y = msc->touches[id].scroll_y - y;
+               int step_hr = ((64 - (int)scroll_speed) * msc->scroll_accel) /
+                             SCROLL_HR_STEPS;
+               int step_x_hr = msc->touches[id].scroll_x_hr - x;
+               int step_y_hr = msc->touches[id].scroll_y_hr - y;
 
                /* Calculate and apply the scroll motion. */
                switch (state) {
                case TOUCH_STATE_START:
                        msc->touches[id].scroll_x = x;
                        msc->touches[id].scroll_y = y;
+                       msc->touches[id].scroll_x_hr = x;
+                       msc->touches[id].scroll_y_hr = y;
 
                        /* Reset acceleration after half a second. */
                        if (scroll_acceleration && time_before(now,
@@ -280,6 +291,24 @@ static void magicmouse_emit_touch(struct magicmouse_sc *msc, int raw_id, u8 *tda
                                msc->scroll_jiffies = now;
                                input_report_rel(input, REL_WHEEL, step_y);
                        }
+
+                       step_x_hr /= step_hr;
+                       if (step_x_hr != 0) {
+                               msc->touches[id].scroll_x_hr -= step_x_hr *
+                                       step_hr;
+                               input_report_rel(input,
+                                                REL_HWHEEL_HI_RES,
+                                                -step_x_hr * SCROLL_HR_MULT);
+                       }
+
+                       step_y_hr /= step_hr;
+                       if (step_y_hr != 0) {
+                               msc->touches[id].scroll_y_hr -= step_y_hr *
+                                       step_hr;
+                               input_report_rel(input,
+                                                REL_WHEEL_HI_RES,
+                                                step_y_hr * SCROLL_HR_MULT);
+                       }
                        break;
                }
        }
@@ -481,6 +510,8 @@ static int magicmouse_setup_input(struct input_dev *input, struct hid_device *hd
                if (emulate_scroll_wheel) {
                        __set_bit(REL_WHEEL, input->relbit);
                        __set_bit(REL_HWHEEL, input->relbit);
+                       __set_bit(REL_WHEEL_HI_RES, input->relbit);
+                       __set_bit(REL_HWHEEL_HI_RES, input->relbit);
                }
        } else if (input->id.product == USB_DEVICE_ID_APPLE_MAGICTRACKPAD2) {
                /* setting the device name to ensure the same driver settings