1 files changed, 36 insertions, 0 deletions

diff --git a/drivers/input/ff-memless.c b/drivers/input/ff-memless.c
index 9667a5fd6bd7..f967008f332e 100644
--- a/drivers/input/ff-memless.c
+++ b/drivers/input/ff-memless.c
@@ -221,6 +221,22 @@ static int get_compatible_type(struct ff_device *ff, int effect_type)
 }
 
 /*
+ * Only left/right direction should be used (under/over 0x8000) for
+ * forward/reverse motor direction (to keep calculation fast & simple).
+ */
+static u16 ml_calculate_direction(u16 direction, u16 force,
+                                  u16 new_direction, u16 new_force)
+{
+        if (!force)
+                return new_direction;
+        if (!new_force)
+                return direction;
+        return (((u32)(direction >> 1) * force +
+                 (new_direction >> 1) * new_force) /
+                (force + new_force)) << 1;
+}
+
+/*
  * Combine two effects and apply gain.
  */
 static void ml_combine_effects(struct ff_effect *effect,
@@ -254,6 +270,19 @@ static void ml_combine_effects(struct ff_effect *effect,
         case FF_RUMBLE:
                 strong = (u32)new->u.rumble.strong_magnitude * gain / 0xffff;
                 weak = (u32)new->u.rumble.weak_magnitude * gain / 0xffff;
+
+                if (effect->u.rumble.strong_magnitude + strong)
+                        effect->direction = ml_calculate_direction(
+                                effect->direction,
+                                effect->u.rumble.strong_magnitude,
+                                new->direction, strong);
+                else if (effect->u.rumble.weak_magnitude + weak)
+                        effect->direction = ml_calculate_direction(
+                                effect->direction,
+                                effect->u.rumble.weak_magnitude,
+                                new->direction, weak);
+                else
+                        effect->direction = 0;
                 effect->u.rumble.strong_magnitude =
                         min(strong + effect->u.rumble.strong_magnitude,
                             0xffffU);
@@ -268,6 +297,13 @@ static void ml_combine_effects(struct ff_effect *effect,
                 /* here we also scale it 0x7fff => 0xffff */
                 i = i * gain / 0x7fff;
 
+                if (effect->u.rumble.strong_magnitude + i)
+                        effect->direction = ml_calculate_direction(
+                                effect->direction,
+                                effect->u.rumble.strong_magnitude,
+                                new->direction, i);
+                else
+                        effect->direction = 0;
                 effect->u.rumble.strong_magnitude =
                         min(i + effect->u.rumble.strong_magnitude, 0xffffU);
                 effect->u.rumble.weak_magnitude =