diff --git a/include/hardware/audio_amplifier.h b/include/hardware/audio_amplifier.h
new file mode 120000
index 0000000..18a66ec
--- /dev/null
+++ b/include/hardware/audio_amplifier.h
@@ -0,0 +1 @@
+../../include_all/hardware/audio_amplifier.h
\ No newline at end of file
diff --git a/include_all/hardware/audio_amplifier.h b/include_all/hardware/audio_amplifier.h
new file mode 100644
index 0000000..4b6f634
--- /dev/null
+++ b/include_all/hardware/audio_amplifier.h
@@ -0,0 +1,168 @@
+/*
+ * Copyright (C) 2015, The CyanogenMod Project
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *      http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+#ifndef CM_AUDIO_AMPLIFIER_INTERFACE_H
+#define CM_AUDIO_AMPLIFIER_INTERFACE_H
+
+#include <stdint.h>
+#include <sys/cdefs.h>
+#include <sys/types.h>
+
+#include <hardware/audio.h>
+#include <hardware/hardware.h>
+
+#include <system/audio.h>
+
+__BEGIN_DECLS
+
+#define AMPLIFIER_HARDWARE_MODULE_ID "audio_amplifier"
+
+#define AMPLIFIER_HARDWARE_INTERFACE "audio_amplifier_hw_if"
+
+#define AMPLIFIER_MODULE_API_VERSION_0_1 HARDWARE_MODULE_API_VERSION(0, 1)
+
+#define AMPLIFIER_DEVICE_API_VERSION_1_0 HARDWARE_DEVICE_API_VERSION(1, 0)
+#define AMPLIFIER_DEVICE_API_VERSION_2_0 HARDWARE_DEVICE_API_VERSION(2, 0)
+#define AMPLIFIER_DEVICE_API_VERSION_2_1 HARDWARE_DEVICE_API_VERSION(2, 1)
+#define AMPLIFIER_DEVICE_API_VERSION_CURRENT AMPLIFIER_DEVICE_API_VERSION_2_1
+
+struct str_parms;
+
+typedef struct amplifier_device {
+    /**
+     * Common methods of the amplifier device. This *must* be the first member
+     * of amplifier_device as users of this structure will cast a hw_device_t
+     * to amplifier_device pointer in contexts where it's known
+     * the hw_device_t references a amplifier_device.
+     */
+    struct hw_device_t common;
+
+    /**
+     * Notify amplifier device of current input devices
+     *
+     * This function should handle only input devices.
+     */
+    int (*set_input_devices)(struct amplifier_device *device, uint32_t devices);
+
+    /**
+     * Notify amplifier device of current output devices
+     *
+     * This function should handle only output devices.
+     */
+    int (*set_output_devices)(struct amplifier_device *device, uint32_t devices);
+
+    /**
+     * Notify amplifier device of output device enable/disable
+     *
+     * This function should handle only output devices.
+     */
+    int (*enable_output_devices)(struct amplifier_device *device,
+            uint32_t devices, bool enable);
+
+    /**
+     * Notify amplifier device of input device enable/disable
+     *
+     * This function should handle only input devices.
+     */
+    int (*enable_input_devices)(struct amplifier_device *device,
+            uint32_t devices, bool enable);
+
+    /**
+     * Notify amplifier device about current audio mode
+     */
+    int (*set_mode)(struct amplifier_device *device, audio_mode_t mode);
+
+    /**
+     * Notify amplifier device that an output stream has started
+     */
+    int (*output_stream_start)(struct amplifier_device *device,
+            struct audio_stream_out *stream, bool offload);
+
+    /**
+     * Notify amplifier device that an input stream has started
+     */
+    int (*input_stream_start)(struct amplifier_device *device,
+            struct audio_stream_in *stream);
+
+    /**
+     * Notify amplifier device that an output stream has stopped
+     */
+    int (*output_stream_standby)(struct amplifier_device *device,
+            struct audio_stream_out *stream);
+
+    /**
+     * Notify amplifier device that an input stream has stopped
+     */
+    int (*input_stream_standby)(struct amplifier_device *device,
+            struct audio_stream_in *stream);
+
+    /**
+     * set/get audio device parameters.
+     */
+    int (*set_parameters)(struct amplifier_device *device,
+        struct str_parms *parms);
+
+    /**
+     * set/get output stream parameters.
+     */
+    int (*out_set_parameters)(struct amplifier_device *device,
+        struct str_parms *parms);
+
+    /**
+     * set/get input stream parameters.
+     */
+    int (*in_set_parameters)(struct amplifier_device *device,
+        struct str_parms *parms);
+
+    /**
+     * set feedback
+     */
+    int (*set_feedback)(struct amplifier_device *device,
+        void *adev, uint32_t devices, bool enable);
+
+    /**
+     * Amplifier calibration
+     */
+    int (*calibrate)(void *adev);
+} amplifier_device_t;
+
+typedef struct amplifier_module {
+    /**
+     * Common methods of the amplifier module. This *must* be the first member
+     * of amplifier_module as users of this structure will cast a hw_module_t
+     * to amplifier_module pointer in contexts where it's known
+     * the hw_module_t references a amplifier_module.
+     */
+    struct hw_module_t common;
+} amplifier_module_t;
+
+/** convenience API for opening and closing a supported device */
+
+static inline int amplifier_device_open(const struct hw_module_t *module,
+        struct amplifier_device **device)
+{
+    return module->methods->open(module, AMPLIFIER_HARDWARE_INTERFACE,
+            (struct hw_device_t **) device);
+}
+
+static inline int amplifier_device_close(struct amplifier_device *device)
+{
+    return device->common.close(&device->common);
+}
+
+__END_DECLS
+
+#endif  // CM_AUDIO_AMPLIFIER_INTERFACE_H
diff --git a/include_all/hardware/hwcomposer_defs.h b/include_all/hardware/hwcomposer_defs.h
index 3823765..c4d8a44 100644
--- a/include_all/hardware/hwcomposer_defs.h
+++ b/include_all/hardware/hwcomposer_defs.h
@@ -299,10 +299,19 @@
 enum {
     HWC_DISPLAY_PRIMARY     = 0,
     HWC_DISPLAY_EXTERNAL    = 1,    // HDMI, DP, etc.
-    HWC_DISPLAY_VIRTUAL     = 2,
 
-    HWC_NUM_PHYSICAL_DISPLAY_TYPES = 2,
-    HWC_NUM_DISPLAY_TYPES          = 3,
+    HWC_DISPLAY_EXTERNAL_2  = 2,
+    HWC_DISPLAY_EXTERNAL_3  = 3,
+    HWC_DISPLAY_EXTERNAL_4  = 4,
+
+    HWC_DISPLAY_BUILTIN_2   = 5,
+    HWC_DISPLAY_BUILTIN_3   = 6,
+    HWC_DISPLAY_BUILTIN_4   = 7,
+
+    HWC_DISPLAY_VIRTUAL     = 8,
+
+    HWC_NUM_PHYSICAL_DISPLAY_TYPES = 8,
+    HWC_NUM_DISPLAY_TYPES          = 9,
 };
 
 enum {
diff --git a/modules/audio/Android.bp b/modules/audio/Android.bp
index 1b34336..12de12b 100644
--- a/modules/audio/Android.bp
+++ b/modules/audio/Android.bp
@@ -70,3 +70,20 @@
     ],
     cflags: ["-Wall", "-Werror", "-Wno-unused-parameter"],
 }
+
+// The stub audio amplifier HAL module that can be used as a skeleton for
+// new implementations.
+cc_library_shared {
+    name: "audio_amplifier.default",
+    relative_install_path: "hw",
+    proprietary: true,
+    srcs: ["audio_amplifier.c"],
+    header_libs: [
+        "libhardware_headers",
+    ],
+    shared_libs: [
+        "libcutils",
+        "liblog",
+    ],
+    cflags: ["-Wall", "-Werror", "-Wno-unused-parameter"],
+}
diff --git a/modules/audio/audio_amplifier.c b/modules/audio/audio_amplifier.c
new file mode 100644
index 0000000..7837b4d
--- /dev/null
+++ b/modules/audio/audio_amplifier.c
@@ -0,0 +1,167 @@
+/*
+ * Copyright (C) 2015 The CyanogenMod Open Source Project
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *      http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+#define LOG_TAG "amplifier_default"
+//#define LOG_NDEBUG 0
+
+#include <stdint.h>
+#include <stdlib.h>
+#include <sys/types.h>
+
+#include <cutils/log.h>
+#include <cutils/str_parms.h>
+
+#include <hardware/audio_amplifier.h>
+#include <hardware/hardware.h>
+
+static int amp_set_input_devices(amplifier_device_t *device, uint32_t devices)
+{
+    return 0;
+}
+
+static int amp_set_output_devices(amplifier_device_t *device, uint32_t devices)
+{
+    return 0;
+}
+
+static int amp_enable_output_devices(amplifier_device_t *device,
+        uint32_t devices, bool enable)
+{
+    return 0;
+}
+
+static int amp_enable_input_devices(amplifier_device_t *device,
+        uint32_t devices, bool enable)
+{
+    return 0;
+}
+
+static int amp_set_mode(amplifier_device_t *device, audio_mode_t mode)
+{
+    return 0;
+}
+
+static int amp_output_stream_start(amplifier_device_t *device,
+        struct audio_stream_out *stream, bool offload)
+{
+    return 0;
+}
+
+static int amp_input_stream_start(amplifier_device_t *device,
+        struct audio_stream_in *stream)
+{
+    return 0;
+}
+
+static int amp_output_stream_standby(amplifier_device_t *device,
+        struct audio_stream_out *stream)
+{
+    return 0;
+}
+
+static int amp_input_stream_standby(amplifier_device_t *device,
+        struct audio_stream_in *stream)
+{
+    return 0;
+}
+
+static int amp_set_parameters(struct amplifier_device *device,
+        struct str_parms *parms)
+{
+    return 0;
+}
+
+static int amp_out_set_parameters(struct amplifier_device *device,
+        struct str_parms *parms)
+{
+    return 0;
+}
+
+static int amp_in_set_parameters(struct amplifier_device *device,
+        struct str_parms *parms)
+{
+    return 0;
+}
+
+static int amp_set_feedback(struct amplifier_device *device,
+        void *adev, uint32_t devices, bool enable)
+{
+    return 0;
+}
+
+static int amp_dev_close(hw_device_t *device)
+{
+    if (device)
+        free(device);
+
+    return 0;
+}
+
+static int amp_module_open(const hw_module_t *module, const char *name,
+        hw_device_t **device)
+{
+    if (strcmp(name, AMPLIFIER_HARDWARE_INTERFACE)) {
+        ALOGE("%s:%d: %s does not match amplifier hardware interface name\n",
+                __func__, __LINE__, name);
+        return -ENODEV;
+    }
+
+    amplifier_device_t *amp_dev = calloc(1, sizeof(amplifier_device_t));
+    if (!amp_dev) {
+        ALOGE("%s:%d: Unable to allocate memory for amplifier device\n",
+                __func__, __LINE__);
+        return -ENOMEM;
+    }
+
+    amp_dev->common.tag = HARDWARE_DEVICE_TAG;
+    amp_dev->common.module = (hw_module_t *) module;
+    amp_dev->common.version = HARDWARE_DEVICE_API_VERSION(1, 0);
+    amp_dev->common.close = amp_dev_close;
+
+    amp_dev->set_input_devices = amp_set_input_devices;
+    amp_dev->set_output_devices = amp_set_output_devices;
+    amp_dev->enable_output_devices = amp_enable_output_devices;
+    amp_dev->enable_input_devices = amp_enable_input_devices;
+    amp_dev->set_mode = amp_set_mode;
+    amp_dev->output_stream_start = amp_output_stream_start;
+    amp_dev->input_stream_start = amp_input_stream_start;
+    amp_dev->output_stream_standby = amp_output_stream_standby;
+    amp_dev->input_stream_standby = amp_input_stream_standby;
+    amp_dev->set_parameters = amp_set_parameters;
+    amp_dev->out_set_parameters = amp_out_set_parameters;
+    amp_dev->in_set_parameters = amp_in_set_parameters;
+    amp_dev->set_feedback = amp_set_feedback;
+
+    *device = (hw_device_t *) amp_dev;
+
+    return 0;
+}
+
+static struct hw_module_methods_t hal_module_methods = {
+    .open = amp_module_open,
+};
+
+amplifier_module_t HAL_MODULE_INFO_SYM = {
+    .common = {
+        .tag = HARDWARE_MODULE_TAG,
+        .module_api_version = AMPLIFIER_MODULE_API_VERSION_0_1,
+        .hal_api_version = HARDWARE_HAL_API_VERSION,
+        .id = AMPLIFIER_HARDWARE_MODULE_ID,
+        .name = "Default audio amplifier HAL",
+        .author = "The CyanogenMod Open Source Project",
+        .methods = &hal_module_methods,
+    },
+};