diff --git a/include/android/input.h b/include/android/input.h
index 5ab4e29..5eeb7fc 100644
--- a/include/android/input.h
+++ b/include/android/input.h
@@ -644,6 +644,13 @@
      */
     AMOTION_EVENT_AXIS_TILT = 25,
     /**
+     * Axis constant:  Generic scroll axis of a motion event.
+     *
+     * - This is used for scroll axis motion events that can't be classified as strictly
+     *   vertical or horizontal. The movement of a rotating scroller is an example of this.
+     */
+    AMOTION_EVENT_AXIS_SCROLL = 26,
+    /**
      * Axis constant: Generic 1 axis of a motion event.
      * The interpretation of a generic axis is device-specific.
      */
@@ -817,6 +824,8 @@
     AINPUT_SOURCE_TOUCH_NAVIGATION = 0x00200000 | AINPUT_SOURCE_CLASS_NONE,
     /** joystick */
     AINPUT_SOURCE_JOYSTICK = 0x01000000 | AINPUT_SOURCE_CLASS_JOYSTICK,
+    /** rotary encoder */
+    AINPUT_SOURCE_ROTARY_ENCODER = 0x00400000 | AINPUT_SOURCE_CLASS_NONE,
 
     /** any */
     AINPUT_SOURCE_ANY = 0xffffff00,
diff --git a/services/inputflinger/EventHub.cpp b/services/inputflinger/EventHub.cpp
index 6b60c7c..98cfe2b 100644
--- a/services/inputflinger/EventHub.cpp
+++ b/services/inputflinger/EventHub.cpp
@@ -1177,6 +1177,15 @@
         device->classes |= INPUT_DEVICE_CLASS_CURSOR;
     }
 
+    // See if this is a rotary encoder type device.
+    String8 deviceType = String8();
+    if (device->configuration &&
+        device->configuration->tryGetProperty(String8("device.type"), deviceType)) {
+            if (!deviceType.compare(String8("rotaryEncoder"))) {
+                device->classes |= INPUT_DEVICE_CLASS_ROTARY_ENCODER;
+            }
+    }
+
     // See if this is a touch pad.
     // Is this a new modern multi-touch driver?
     if (test_bit(ABS_MT_POSITION_X, device->absBitmask)
diff --git a/services/inputflinger/EventHub.h b/services/inputflinger/EventHub.h
index 3ec4910..7c3e11e 100644
--- a/services/inputflinger/EventHub.h
+++ b/services/inputflinger/EventHub.h
@@ -137,6 +137,9 @@
     /* The input device is an external stylus (has data we want to fuse with touch data). */
     INPUT_DEVICE_CLASS_EXTERNAL_STYLUS = 0x00000800,
 
+    /* The input device has a rotary encoder */
+    INPUT_DEVICE_CLASS_ROTARY_ENCODER = 0x00001000,
+
     /* The input device is virtual (not a real device, not part of UI configuration). */
     INPUT_DEVICE_CLASS_VIRTUAL       = 0x40000000,
 
diff --git a/services/inputflinger/InputReader.cpp b/services/inputflinger/InputReader.cpp
index 36095bf..d7329d9 100644
--- a/services/inputflinger/InputReader.cpp
+++ b/services/inputflinger/InputReader.cpp
@@ -450,6 +450,11 @@
         device->addMapper(new SwitchInputMapper(device));
     }
 
+    // Scroll wheel-like devices.
+    if (classes & INPUT_DEVICE_CLASS_ROTARY_ENCODER) {
+        device->addMapper(new RotaryEncoderInputMapper(device));
+    }
+
     // Vibrator-like devices.
     if (classes & INPUT_DEVICE_CLASS_VIBRATOR) {
         device->addMapper(new VibratorInputMapper(device));
@@ -2718,6 +2723,92 @@
     }
 }
 
+// --- RotaryEncoderInputMapper ---
+
+RotaryEncoderInputMapper::RotaryEncoderInputMapper(InputDevice* device) :
+        InputMapper(device) {
+    mSource = AINPUT_SOURCE_ROTARY_ENCODER;
+}
+
+RotaryEncoderInputMapper::~RotaryEncoderInputMapper() {
+}
+
+uint32_t RotaryEncoderInputMapper::getSources() {
+    return mSource;
+}
+
+void RotaryEncoderInputMapper::populateDeviceInfo(InputDeviceInfo* info) {
+    InputMapper::populateDeviceInfo(info);
+
+    if (mRotaryEncoderScrollAccumulator.haveRelativeVWheel()) {
+        info->addMotionRange(AMOTION_EVENT_AXIS_SCROLL, mSource, -1.0f, 1.0f, 0.0f, 0.0f, 0.0f);
+    }
+}
+
+void RotaryEncoderInputMapper::dump(String8& dump) {
+    dump.append(INDENT2 "Rotary Encoder Input Mapper:\n");
+    dump.appendFormat(INDENT3 "HaveWheel: %s\n",
+            toString(mRotaryEncoderScrollAccumulator.haveRelativeVWheel()));
+}
+
+void RotaryEncoderInputMapper::configure(nsecs_t when,
+        const InputReaderConfiguration* config, uint32_t changes) {
+    InputMapper::configure(when, config, changes);
+    if (!changes) {
+        mRotaryEncoderScrollAccumulator.configure(getDevice());
+    }
+}
+
+void RotaryEncoderInputMapper::reset(nsecs_t when) {
+    mRotaryEncoderScrollAccumulator.reset(getDevice());
+
+    InputMapper::reset(when);
+}
+
+void RotaryEncoderInputMapper::process(const RawEvent* rawEvent) {
+    mRotaryEncoderScrollAccumulator.process(rawEvent);
+
+    if (rawEvent->type == EV_SYN && rawEvent->code == SYN_REPORT) {
+        sync(rawEvent->when);
+    }
+}
+
+void RotaryEncoderInputMapper::sync(nsecs_t when) {
+    PointerCoords pointerCoords;
+    pointerCoords.clear();
+
+    PointerProperties pointerProperties;
+    pointerProperties.clear();
+    pointerProperties.id = 0;
+    pointerProperties.toolType = AMOTION_EVENT_TOOL_TYPE_UNKNOWN;
+
+    float scroll = mRotaryEncoderScrollAccumulator.getRelativeVWheel();
+    bool scrolled = scroll != 0;
+
+    // This is not a pointer, so it's not associated with a display.
+    int32_t displayId = ADISPLAY_ID_NONE;
+
+    // Moving the rotary encoder should wake the device (if specified).
+    uint32_t policyFlags = 0;
+    if (scrolled && getDevice()->isExternal()) {
+        policyFlags |= POLICY_FLAG_WAKE;
+    }
+
+    // Send motion event.
+    if (scrolled) {
+        int32_t metaState = mContext->getGlobalMetaState();
+        pointerCoords.setAxisValue(AMOTION_EVENT_AXIS_SCROLL, scroll);
+
+        NotifyMotionArgs scrollArgs(when, getDeviceId(), mSource, policyFlags,
+                AMOTION_EVENT_ACTION_SCROLL, 0, 0, metaState, 0,
+                AMOTION_EVENT_EDGE_FLAG_NONE,
+                displayId, 1, &pointerProperties, &pointerCoords,
+                0, 0, 0);
+        getListener()->notifyMotion(&scrollArgs);
+    }
+
+    mRotaryEncoderScrollAccumulator.finishSync();
+}
 
 // --- TouchInputMapper ---
 
diff --git a/services/inputflinger/InputReader.h b/services/inputflinger/InputReader.h
index 7cb4680..58db3dc 100644
--- a/services/inputflinger/InputReader.h
+++ b/services/inputflinger/InputReader.h
@@ -1232,6 +1232,26 @@
 };
 
 
+class RotaryEncoderInputMapper : public InputMapper {
+public:
+    RotaryEncoderInputMapper(InputDevice* device);
+    virtual ~RotaryEncoderInputMapper();
+
+    virtual uint32_t getSources();
+    virtual void populateDeviceInfo(InputDeviceInfo* deviceInfo);
+    virtual void dump(String8& dump);
+    virtual void configure(nsecs_t when, const InputReaderConfiguration* config, uint32_t changes);
+    virtual void reset(nsecs_t when);
+    virtual void process(const RawEvent* rawEvent);
+
+private:
+    CursorScrollAccumulator mRotaryEncoderScrollAccumulator;
+
+    int32_t mSource;
+
+    void sync(nsecs_t when);
+};
+
 class TouchInputMapper : public InputMapper {
 public:
     TouchInputMapper(InputDevice* device);