[PATCH 3/5] HID: magicmouse: properly account for scroll movement in state

[Chase Douglas]

Before this change, sequential scroll events would take a variable
amount of movement due to incorrect accounting. This change ensures all
scroll movements require a deterministic touch movement for an action to
occur.

Signed-off-by: Chase Douglas <chase.douglas at canonical.com>
Acked-by: Michael Poole <mdpoole at troilus.org>
Signed-off-by: Jiri Kosina <jkosina at suse.cz>
(cherry picked from commit 8d93efb27ab8927ffc7a357f1b2d10039de50ed4
from git://git.kernel.org/pub/scm/linux/kernel/git/jikos/hid.git)
---
 drivers/hid/hid-magicmouse.c |    3 ++-
 1 files changed, 2 insertions(+), 1 deletions(-)

diff --git a/drivers/hid/hid-magicmouse.c b/drivers/hid/hid-magicmouse.c
index 4c4a79c..f44aaf2 100644
--- a/drivers/hid/hid-magicmouse.c
+++ b/drivers/hid/hid-magicmouse.c
@@ -189,7 +189,8 @@ static void magicmouse_emit_touch(struct magicmouse_sc *msc, int raw_id, u8 *tda
 		case TOUCH_STATE_DRAG:
 			step = step / accel_profile[msc->scroll_accel];
 			if (step != 0) {
-				msc->touches[id].scroll_y = y;
+				msc->touches[id].scroll_y -=
+					step * accel_profile[msc->scroll_accel];
 				msc->scroll_jiffies = now;
 				input_report_rel(input, REL_WHEEL, step);
 			}
-- 
1.7.0.4