diff --git a/include/hardware/audio.h b/include/hardware/audio.h
index 29b695c..49cc0fe 100644
--- a/include/hardware/audio.h
+++ b/include/hardware/audio.h
@@ -431,6 +431,23 @@
      * Unit: the number of input audio frames
      */
     uint32_t (*get_input_frames_lost)(struct audio_stream_in *stream);
+
+    /**
+     * Return a recent count of the number of audio frames received and
+     * the clock time associated with that frame count.
+     *
+     * frames is the total frame count received. This should be as early in
+     *     the capture pipeline as possible. In general,
+     *     frames should be non-negative and should not go "backwards".
+     *
+     * time is the clock MONOTONIC time when frames was measured. In general,
+     *     time should be a positive quantity and should not go "backwards".
+     *
+     * The status returned is 0 on success, -ENOSYS if the device is not
+     * ready/available, or -EINVAL if the arguments are null or otherwise invalid.
+     */
+    int (*get_capture_position)(const struct audio_stream_in *stream,
+                                int64_t *frames, int64_t *time);
 };
 typedef struct audio_stream_in audio_stream_in_t;
 
diff --git a/include/hardware/gps.h b/include/hardware/gps.h
index 6fd47a9..68e3052 100644
--- a/include/hardware/gps.h
+++ b/include/hardware/gps.h
@@ -39,10 +39,15 @@
 
 /** Maximum number of SVs for gps_sv_status_callback(). */
 #define GPS_MAX_SVS 32
+/** Maximum number of SVs for gps_sv_status_callback(). */
+#define GNSS_MAX_SVS 64
 
 /** Maximum number of Measurements in gps_measurement_callback(). */
 #define GPS_MAX_MEASUREMENT   32
 
+/** Maximum number of Measurements in gnss_measurement_callback(). */
+#define GNSS_MAX_MEASUREMENT   64
+
 /** Requested operational mode for GPS operation. */
 typedef uint32_t GpsPositionMode;
 // IMPORTANT: Note that the following values must match
@@ -524,7 +529,7 @@
      * - Galileo: 1-25
      * - Beidou:  1-35
      */
-    int prn;
+    int16_t svid;
 
     /** Signal to noise ratio. */
     float snr;
@@ -550,63 +555,36 @@
 } GnssSvInfo;
 
 /**
- * Represents SV status.
- *
- * When switching from pre-N to N version of GpsSvStatus:
- *
- * 1) Fill in the fields from num_svs through used_in_fix_mask the same way as
- * was done before, e.g. using the range of 65-88 to report Glonass info,
- * 201-235 for Beidou, etc. (but with no used_in_fix_mask info - those are
- * index by prn, and thus for GPS only). This will help ensure compatibility
- * when a newer GPS HAL is used with an older version of Android.
- *
- * 2) Fill in the gnss_sv_list with information about SVs from all
- * constellations (GPS & other GNSS's) - when this is filled in, this will be
- * the only source of information about satellite status (e.g. for working with
- * GpsStatus facing applications), the earlier fields will be ignored.
+ * Legacy struct to represents SV status.
+ * Deprecated, to be removed in the next Android release.
+ * Use GnssSvStatus instead.
  */
 typedef struct {
     /** set to sizeof(GpsSvStatus) */
     size_t size;
+    int num_svs;
+    GpsSvInfo sv_list[GPS_MAX_SVS];
+    uint32_t ephemeris_mask;
+    uint32_t almanac_mask;
+    uint32_t used_in_fix_mask;
+} GpsSvStatus;
+
+/**
+ * Represents SV status.
+ */
+typedef struct {
+    /** set to sizeof(GnssSvStatus) */
+    size_t size;
 
     /** Number of GPS SVs currently visible, refers to the SVs stored in sv_list */
     int num_svs;
-
-    /** Contains an array of GPS SV information in legacy GPS format. */
-    GpsSvInfo sv_list[GPS_MAX_SVS];
-
-    /**
-     * Represents a bit mask indicating which GPS SVs have ephemeris data,
-     * refers to sv_list.
-     */
-    uint32_t ephemeris_mask;
-
-    /**
-     * Represents a bit mask indicating which GPS SVs have almanac data, refers
-     * to sv_list.
-     */
-    uint32_t almanac_mask;
-
-    /**
-     * Represents a bit mask indicating which GPS SVs
-     * were used for computing the most recent position fix,
-     * refers to sv_list.
-     */
-    uint32_t used_in_fix_mask;
-
-    /**
-     * Size of the array which contains SV info for all GNSS constellation
-     * except for GPS.
-     */
-    size_t gnss_sv_list_size;
-
     /**
      * Pointer to an array of SVs information for all GNSS constellations,
      * except GPS, which is reported using sv_list
      */
-    GnssSvInfo* gnss_sv_list;
+    GnssSvInfo gnss_sv_list[GNSS_MAX_SVS];
 
-} GpsSvStatus;
+} GnssSvStatus;
 
 /* CellID for 2G, 3G and LTE, used in AGPS. */
 typedef struct {
@@ -660,6 +638,12 @@
 typedef void (* gps_sv_status_callback)(GpsSvStatus* sv_info);
 
 /**
+ * Callback with SV status information.
+ * Can only be called from a thread created by create_thread_cb.
+ */
+typedef void (* gnss_sv_status_callback)(GnssSvStatus* sv_info);
+
+/**
  * Callback for reporting NMEA sentences. Can only be called from a thread
  * created by create_thread_cb.
  */
@@ -715,24 +699,6 @@
  */
 typedef void (*gps_set_system_info)(const GpsSystemInfo* info);
 
-/**
- * Legacy GPS callback structure.
- * See GpsCallbacks for more information.
- */
-typedef struct {
-    /** set to sizeof(GpsCallbacks_v1) */
-    size_t      size;
-    gps_location_callback location_cb;
-    gps_status_callback status_cb;
-    gps_sv_status_callback sv_status_cb;
-    gps_nmea_callback nmea_cb;
-    gps_set_capabilities set_capabilities_cb;
-    gps_acquire_wakelock acquire_wakelock_cb;
-    gps_release_wakelock release_wakelock_cb;
-    gps_create_thread create_thread_cb;
-    gps_request_utc_time request_utc_time_cb;
-} GpsCallbacks_v1;
-
 /** New GPS callback structure. */
 typedef struct {
     /** set to sizeof(GpsCallbacks) */
@@ -747,15 +713,8 @@
     gps_create_thread create_thread_cb;
     gps_request_utc_time request_utc_time_cb;
 
-    /**
-     * Callback for the chipset to report system information.
-     *
-     * This field is newly introduced since N. The driver implementation must
-     * check 'size' field against 'sizeof(GpsCallbacks)' and
-     * 'sizeof(GpsCallbacks_v1)' to decide whether the new field is valid before
-     * calling it.
-     */
     gps_set_system_info set_system_info_cb;
+    gnss_sv_status_callback gnss_sv_status_cb;
 } GpsCallbacks;
 
 /** Represents the standard GPS interface. */
@@ -1402,11 +1361,31 @@
 } GpsGeofencingInterface;
 
 /**
- * Represents an estimate of the GPS clock time.
+ * Legacy struct to represent an estimate of the GPS clock time.
+ * Deprecated, to be removed in the next Android release.
+ * Use GnssClock instead.
  */
 typedef struct {
     /** set to sizeof(GpsClock) */
     size_t size;
+    GpsClockFlags flags;
+    int16_t leap_second;
+    GpsClockType type;
+    int64_t time_ns;
+    double time_uncertainty_ns;
+    int64_t full_bias_ns;
+    double bias_ns;
+    double bias_uncertainty_ns;
+    double drift_nsps;
+    double drift_uncertainty_nsps;
+} GpsClock;
+
+/**
+ * Represents an estimate of the GPS clock time.
+ */
+typedef struct {
+    /** set to sizeof(GnssClock) */
+    size_t size;
 
     /** A set of flags indicating the validity of the fields in this data structure. */
     GpsClockFlags flags;
@@ -1538,10 +1517,53 @@
      * re-solve for the clock bias and drift.
      */
     int64_t time_of_last_hw_clock_discontinuity_ns;
-} GpsClock;
+} GnssClock;
 
 /**
- * Represents a GPS Measurement, it contains raw and computed information.
+ * Legacy struct to represent a GPS Measurement, it contains raw and computed
+ * information.
+ * Deprecated, to be removed in the next Android release.
+ * Use GnssMeasurement instead.
+ */
+typedef struct {
+    /** set to sizeof(GpsMeasurement) */
+    size_t size;
+    GpsMeasurementFlags flags;
+    int8_t prn;
+    double time_offset_ns;
+    GpsMeasurementState state;
+    int64_t received_gps_tow_ns;
+    int64_t received_gps_tow_uncertainty_ns;
+    double c_n0_dbhz;
+    double pseudorange_rate_mps;
+    double pseudorange_rate_uncertainty_mps;
+    GpsAccumulatedDeltaRangeState accumulated_delta_range_state;
+    double accumulated_delta_range_m;
+    double accumulated_delta_range_uncertainty_m;
+    double pseudorange_m;
+    double pseudorange_uncertainty_m;
+    double code_phase_chips;
+    double code_phase_uncertainty_chips;
+    float carrier_frequency_hz;
+    int64_t carrier_cycles;
+    double carrier_phase;
+    double carrier_phase_uncertainty;
+    GpsLossOfLock loss_of_lock;
+    int32_t bit_number;
+    int16_t time_from_last_bit_ms;
+    double doppler_shift_hz;
+    double doppler_shift_uncertainty_hz;
+    GpsMultipathIndicator multipath_indicator;
+    double snr_db;
+    double elevation_deg;
+    double elevation_uncertainty_deg;
+    double azimuth_deg;
+    double azimuth_uncertainty_deg;
+    bool used_in_fix;
+} GpsMeasurement;
+
+/**
+ * Represents a GNSS Measurement, it contains raw and computed information.
  */
 typedef struct {
     /** set to sizeof(GpsMeasurement) */
@@ -1551,10 +1573,10 @@
     GpsMeasurementFlags flags;
 
     /**
-     * Pseudo-random number in the range of [1, 32]
+     * Satellite vehicle ID number, as defined in GnssSvInfo::svid
      * This is a mandatory value.
      */
-    int8_t prn;
+    int16_t svid;
 
     /**
      * Time offset at which the measurement was taken in nanoseconds.
@@ -1858,22 +1880,37 @@
      */
     double pseudorange_rate_carrier_uncertainty_mps;
 
-} GpsMeasurement;
+} GnssMeasurement;
+
+/**
+ * Legacy struct to represents a reading of GPS measurements.
+ * Deprecated, to be removed in the next Android release.
+ * Use GnssData instead.
+ */
+typedef struct {
+    /** set to sizeof(GpsData) */
+    size_t size;
+    size_t measurement_count;
+    GpsMeasurement measurements[GPS_MAX_MEASUREMENT];
+
+    /** The GPS clock time reading. */
+    GpsClock clock;
+} GpsData;
 
 /** Represents a reading of GPS measurements. */
 typedef struct {
-    /** set to sizeof(GpsData) */
+    /** set to sizeof(GnssData) */
     size_t size;
 
     /** Number of measurements. */
     size_t measurement_count;
 
     /** The array of measurements. */
-    GpsMeasurement measurements[GPS_MAX_MEASUREMENT];
+    GnssMeasurement measurements[GNSS_MAX_MEASUREMENT];
 
     /** The GPS clock time reading. */
-    GpsClock clock;
-} GpsData;
+    GnssClock clock;
+} GnssData;
 
 /**
  * The callback for to report measurements from the HAL.
@@ -1883,10 +1920,19 @@
  */
 typedef void (*gps_measurement_callback) (GpsData* data);
 
+/**
+ * The callback for to report measurements from the HAL.
+ *
+ * Parameters:
+ *    data - A data structure containing the measurements.
+ */
+typedef void (*gnss_measurement_callback) (GnssData* data);
+
 typedef struct {
     /** set to sizeof(GpsMeasurementCallbacks) */
     size_t size;
     gps_measurement_callback measurement_callback;
+    gnss_measurement_callback gnss_measurement_callback;
 } GpsMeasurementCallbacks;
 
 #define GPS_MEASUREMENT_OPERATION_SUCCESS          0
@@ -1923,17 +1969,32 @@
 
 } GpsMeasurementInterface;
 
-
-/** Represents a GPS navigation message (or a fragment of it). */
+/**
+ * Legacy struct to represents a GPS navigation message (or a fragment of it).
+ * Deprecated, to be removed in the next Android release.
+ * Use GnssNavigationMessage instead.
+ */
 typedef struct {
     /** set to sizeof(GpsNavigationMessage) */
     size_t size;
+    int8_t prn;
+    GpsNavigationMessageType type;
+    NavigationMessageStatus status;
+    int16_t message_id;
+    int16_t submessage_id;
+    size_t data_length;
+    uint8_t* data;
+} GpsNavigationMessage;
+
+/** Represents a GPS navigation message (or a fragment of it). */
+typedef struct {
+    /** set to sizeof(GnssNavigationMessage) */
+    size_t size;
 
     /**
-     * Pseudo-random number in the range of [1, 32]
      * This is a mandatory value.
      */
-    int8_t prn;
+    int16_t svid;
 
     /**
      * The type of message contained in the structure.
@@ -1982,7 +2043,7 @@
      */
     uint8_t* data;
 
-} GpsNavigationMessage;
+} GnssNavigationMessage;
 
 /**
  * The callback to report an available fragment of a GPS navigation messages from the HAL.
@@ -1992,10 +2053,19 @@
  */
 typedef void (*gps_navigation_message_callback) (GpsNavigationMessage* message);
 
+/**
+ * The callback to report an available fragment of a GPS navigation messages from the HAL.
+ *
+ * Parameters:
+ *      message - The GPS navigation submessage/subframe representation.
+ */
+typedef void (*gnss_navigation_message_callback) (GnssNavigationMessage* message);
+
 typedef struct {
     /** set to sizeof(GpsNavigationMessageCallbacks) */
     size_t size;
     gps_navigation_message_callback navigation_message_callback;
+    gnss_navigation_message_callback gnss_navigation_message_callback;
 } GpsNavigationMessageCallbacks;
 
 #define GPS_NAVIGATION_MESSAGE_OPERATION_SUCCESS             0
diff --git a/include/hardware/gps_internal.h b/include/hardware/gps_internal.h
index cd83636..6a3833b 100644
--- a/include/hardware/gps_internal.h
+++ b/include/hardware/gps_internal.h
@@ -26,18 +26,23 @@
 __BEGIN_DECLS
 
 /**
- * Legacy struct to represent SV status.
- * See GpsSvStatus_v2 for more information.
+ * Legacy GPS callback structure.
+ * Deprecated, to be removed in the next Android release.
+ * Use GpsCallbacks instead.
  */
 typedef struct {
-    /** set to sizeof(GpsSvStatus_v1) */
-    size_t          size;
-    int         num_svs;
-    GpsSvInfo   sv_list[GPS_MAX_SVS];
-    uint32_t    ephemeris_mask;
-    uint32_t    almanac_mask;
-    uint32_t    used_in_fix_mask;
-} GpsSvStatus_v1;
+    /** set to sizeof(GpsCallbacks_v1) */
+    size_t      size;
+    gps_location_callback location_cb;
+    gps_status_callback status_cb;
+    gps_sv_status_callback sv_status_cb;
+    gps_nmea_callback nmea_cb;
+    gps_set_capabilities set_capabilities_cb;
+    gps_acquire_wakelock acquire_wakelock_cb;
+    gps_release_wakelock release_wakelock_cb;
+    gps_create_thread create_thread_cb;
+    gps_request_utc_time request_utc_time_cb;
+} GpsCallbacks_v1;
 
 #pragma pack(push,4)
 // We need to keep the alignment of this data structure to 4-bytes, to ensure that in 64-bit
@@ -86,82 +91,6 @@
     int  (*set_server)( AGpsType type, const char* hostname, int port );
 } AGpsInterface_v1;
 
-/**
- * Legacy struct to represent an estimate of the GPS clock time.
- * See GpsClock_v2 for more details.
- */
-typedef struct {
-    /** set to sizeof(GpsClock_v1) */
-    size_t size;
-    GpsClockFlags flags;
-    int16_t leap_second;
-    GpsClockType type;
-    int64_t time_ns;
-    double time_uncertainty_ns;
-    int64_t full_bias_ns;
-    double bias_ns;
-    double bias_uncertainty_ns;
-    double drift_nsps;
-    double drift_uncertainty_nsps;
-} GpsClock_v1;
-
-/**
- * Legacy struct to represent a GPS Measurement, it contains raw and computed
- * information.
- * See GpsMeasurement_v2 for more details.
- */
-typedef struct {
-    /** set to sizeof(GpsMeasurement_v1) */
-    size_t size;
-    GpsMeasurementFlags flags;
-    int8_t prn;
-    double time_offset_ns;
-    GpsMeasurementState state;
-    int64_t received_gps_tow_ns;
-    int64_t received_gps_tow_uncertainty_ns;
-    double c_n0_dbhz;
-    double pseudorange_rate_mps;
-    double pseudorange_rate_uncertainty_mps;
-    GpsAccumulatedDeltaRangeState accumulated_delta_range_state;
-    double accumulated_delta_range_m;
-    double accumulated_delta_range_uncertainty_m;
-    double pseudorange_m;
-    double pseudorange_uncertainty_m;
-    double code_phase_chips;
-    double code_phase_uncertainty_chips;
-    float carrier_frequency_hz;
-    int64_t carrier_cycles;
-    double carrier_phase;
-    double carrier_phase_uncertainty;
-    GpsLossOfLock loss_of_lock;
-    int32_t bit_number;
-    int16_t time_from_last_bit_ms;
-    double doppler_shift_hz;
-    double doppler_shift_uncertainty_hz;
-    GpsMultipathIndicator multipath_indicator;
-    double snr_db;
-    double elevation_deg;
-    double elevation_uncertainty_deg;
-    double azimuth_deg;
-    double azimuth_uncertainty_deg;
-    bool used_in_fix;
-} GpsMeasurement_v1;
-
-/** Represents a reading of GPS measurements. */
-typedef struct {
-    /** set to sizeof(GpsData_v1) */
-    size_t size;
-
-    /** Number of measurements. */
-    size_t measurement_count;
-
-    /** The array of measurements. */
-    GpsMeasurement_v1 measurements[GPS_MAX_MEASUREMENT];
-
-    /** The GPS clock time reading. */
-    GpsClock_v1 clock;
-} GpsData_v1;
-
 __END_DECLS
 
 #endif /* ANDROID_INCLUDE_HARDWARE_GPS_INTERNAL_H */
diff --git a/include/hardware/keymaster_defs.h b/include/hardware/keymaster_defs.h
index 80b2318..d59f3cb 100644
--- a/include/hardware/keymaster_defs.h
+++ b/include/hardware/keymaster_defs.h
@@ -126,14 +126,15 @@
      * Semantically unenforceable tags, either because they have no specific meaning or because
      * they're informational only.
      */
-    KM_TAG_APPLICATION_DATA = KM_BYTES | 700,  /* Data provided by authorized application. */
-    KM_TAG_CREATION_DATETIME = KM_DATE | 701,  /* Key creation time */
-    KM_TAG_ORIGIN = KM_ENUM | 702,             /* keymaster_key_origin_t. */
-    KM_TAG_ROLLBACK_RESISTANT = KM_BOOL | 703, /* Whether key is rollback-resistant. */
-    KM_TAG_ROOT_OF_TRUST = KM_BYTES | 704,     /* Root of trust ID. */
-    KM_TAG_OS_VERSION = KM_UINT | 705,         /* Version of system (keymaster2) */
-    KM_TAG_OS_PATCHLEVEL = KM_UINT | 706,      /* Patch level of system (keymaster2) */
-    KM_TAG_UNIQUE_ID = KM_BYTES | 707,         /* Used to provide unique ID in attestation */
+    KM_TAG_APPLICATION_DATA = KM_BYTES | 700,      /* Data provided by authorized application. */
+    KM_TAG_CREATION_DATETIME = KM_DATE | 701,      /* Key creation time */
+    KM_TAG_ORIGIN = KM_ENUM | 702,                 /* keymaster_key_origin_t. */
+    KM_TAG_ROLLBACK_RESISTANT = KM_BOOL | 703,     /* Whether key is rollback-resistant. */
+    KM_TAG_ROOT_OF_TRUST = KM_BYTES | 704,         /* Root of trust ID. */
+    KM_TAG_OS_VERSION = KM_UINT | 705,             /* Version of system (keymaster2) */
+    KM_TAG_OS_PATCHLEVEL = KM_UINT | 706,          /* Patch level of system (keymaster2) */
+    KM_TAG_UNIQUE_ID = KM_BYTES | 707,             /* Used to provide unique ID in attestation */
+    KM_TAG_ATTESTATION_CHALLENGE = KM_BYTES | 708, /* Used to provide challenge in attestation */
 
     /* Tags used only to provide data to or receive data from operations */
     KM_TAG_ASSOCIATED_DATA = KM_BYTES | 1000, /* Used to provide associated data for AEAD modes. */
@@ -400,6 +401,7 @@
     KM_ERROR_UNSUPPORTED_KDF = -60,
     KM_ERROR_UNSUPPORTED_EC_CURVE = -61,
     KM_ERROR_KEY_REQUIRES_UPGRADE = -62,
+    KM_ERROR_ATTESTATION_CHALLENGE_MISSING = -63,
 
     KM_ERROR_UNIMPLEMENTED = -100,
     KM_ERROR_VERSION_MISMATCH = -101,
diff --git a/include/hardware/vehicle.h b/include/hardware/vehicle.h
index bd623ab..71c57bc 100644
--- a/include/hardware/vehicle.h
+++ b/include/hardware/vehicle.h
@@ -729,6 +729,8 @@
     VEHICLE_AUDIO_CONTEXT_CD_ROM                         = 0x100,
     /** Aux audio input is played */
     VEHICLE_AUDIO_CONTEXT_AUX_AUDIO                      = 0x200,
+    /** system sound like UI feedback */
+    VEHICLE_AUDIO_CONTEXT_SYSTEM_SOUND                   = 0x400,
 };
 
 /**
diff --git a/modules/soundtrigger/sound_trigger_hw.c b/modules/soundtrigger/sound_trigger_hw.c
index 2c1cc9c..8083b1f 100644
--- a/modules/soundtrigger/sound_trigger_hw.c
+++ b/modules/soundtrigger/sound_trigger_hw.c
@@ -30,7 +30,7 @@
  */
 
 #define LOG_TAG "sound_trigger_hw_default"
-/*#define LOG_NDEBUG 0*/
+#define LOG_NDEBUG 1
 
 #include <errno.h>
 #include <stdio.h>
@@ -51,10 +51,6 @@
 #include <system/sound_trigger.h>
 #include <hardware/sound_trigger.h>
 
-/* Although max_sound_models is specified in sound_trigger_properties, having a maximum maximum
-allows a dramatic simplification of data structures in this file */
-#define MAX_MAX_SOUND_MODELS 5
-
 static const struct sound_trigger_properties hw_properties = {
         "The Android Open Source Project", // implementor
         "Sound Trigger stub HAL", // description
@@ -72,15 +68,19 @@
 };
 
 struct recognition_context {
-      /* Sound Model Information Modified On Load */
-    sound_model_handle_t loaded_sound_model;
-    sound_model_callback_t sound_model_callback;
-    void *sound_model_cookie;
+    // Sound Model information, added in method load_sound_model
+    sound_model_handle_t model_handle;
+    sound_trigger_sound_model_type_t model_type;
+    sound_model_callback_t model_callback;
+    void *model_cookie;
 
-    /* Sound Model Information Modified On Recognition Start */
+    // Sound Model information, added in start_recognition
     struct sound_trigger_recognition_config *config;
     recognition_callback_t recognition_callback;
     void *recognition_cookie;
+
+    // Next recognition_context in the linked list
+    struct recognition_context *next;
 };
 
 struct stub_sound_trigger_device {
@@ -88,7 +88,8 @@
     pthread_mutex_t lock;
     pthread_t callback_thread;
 
-    struct recognition_context model_context[MAX_MAX_SOUND_MODELS];
+    // Recognition contexts are stored as a linked list
+    struct recognition_context *root_model_context;
 
     int next_sound_model_id;
 };
@@ -104,57 +105,94 @@
     return new_id;
 }
 
-static char *sound_trigger_event_alloc(struct stub_sound_trigger_device *stdev,
-                                       sound_model_handle_t handle) {
-    struct sound_trigger_phrase_recognition_event *event;
+static char *sound_trigger_event_alloc(sound_model_handle_t handle,
+            sound_trigger_sound_model_type_t model_type,
+            struct sound_trigger_recognition_config *config) {
     char *data;
-    data = (char *)calloc(1, sizeof(struct sound_trigger_phrase_recognition_event));
-    if (!data)
-        return NULL;
+    if (model_type == SOUND_MODEL_TYPE_KEYPHRASE) {
+        struct sound_trigger_phrase_recognition_event *event;
+        data = (char *)calloc(1, sizeof(struct sound_trigger_phrase_recognition_event));
+        if (!data)
+            return NULL;
+        event = (struct sound_trigger_phrase_recognition_event *)data;
+        event->common.status = RECOGNITION_STATUS_SUCCESS;
+        event->common.type = SOUND_MODEL_TYPE_KEYPHRASE;
+        event->common.model = handle;
 
-    unsigned int model_index;
-    bool found = false;
-    for(model_index = 0; model_index < hw_properties.max_sound_models; model_index++) {
-        if (stdev->model_context[model_index].loaded_sound_model == handle) {
-            found = true;
-            break;
+        if (config) {
+            unsigned int i;
+
+            event->num_phrases = config->num_phrases;
+            if (event->num_phrases > SOUND_TRIGGER_MAX_PHRASES)
+                event->num_phrases = SOUND_TRIGGER_MAX_PHRASES;
+            for (i=0; i < event->num_phrases; i++)
+                memcpy(&event->phrase_extras[i],
+                       &config->phrases[i],
+                       sizeof(struct sound_trigger_phrase_recognition_extra));
         }
-    }
-    if (found == false) {
-        ALOGW("Can't find model");
+
+        event->num_phrases = 1;
+        event->phrase_extras[0].confidence_level = 100;
+        event->phrase_extras[0].num_levels = 1;
+        event->phrase_extras[0].levels[0].level = 100;
+        event->phrase_extras[0].levels[0].user_id = 0;
+        // Signify that all the data is comming through streaming, not through the buffer.
+        event->common.capture_available = true;
+        event->common.audio_config = AUDIO_CONFIG_INITIALIZER;
+        event->common.audio_config.sample_rate = 16000;
+        event->common.audio_config.channel_mask = AUDIO_CHANNEL_IN_MONO;
+        event->common.audio_config.format = AUDIO_FORMAT_PCM_16_BIT;
+    } else if (model_type == SOUND_MODEL_TYPE_GENERIC) {
+        struct sound_trigger_generic_recognition_event *event;
+        data = (char *)calloc(1, sizeof(struct sound_trigger_generic_recognition_event));
+        if (!data)
+            return NULL;
+        event = (struct sound_trigger_generic_recognition_event *)data;
+        event->common.status = RECOGNITION_STATUS_SUCCESS;
+        event->common.type = SOUND_MODEL_TYPE_GENERIC;
+        event->common.model = handle;
+
+        // Signify that all the data is comming through streaming, not through the buffer.
+        event->common.capture_available = true;
+        event->common.audio_config = AUDIO_CONFIG_INITIALIZER;
+        event->common.audio_config.sample_rate = 16000;
+        event->common.audio_config.channel_mask = AUDIO_CHANNEL_IN_MONO;
+        event->common.audio_config.format = AUDIO_FORMAT_PCM_16_BIT;
+    } else {
+        ALOGW("No Valid Event Type Known");
         return NULL;
     }
+    return data;
+}
 
-    event = (struct sound_trigger_phrase_recognition_event *)data;
-    event->common.status = RECOGNITION_STATUS_SUCCESS;
-    event->common.type = SOUND_MODEL_TYPE_KEYPHRASE;
-    event->common.model = handle;
-
-    if (stdev->model_context[model_index].config) {
-        unsigned int i;
-
-        event->num_phrases = stdev->model_context[model_index].config->num_phrases;
-        if (event->num_phrases > SOUND_TRIGGER_MAX_PHRASES)
-            event->num_phrases = SOUND_TRIGGER_MAX_PHRASES;
-        for (i=0; i < event->num_phrases; i++)
-            memcpy(&event->phrase_extras[i], &stdev->model_context[model_index].config->phrases[i],
-                   sizeof(struct sound_trigger_phrase_recognition_extra));
+static void send_recognition_event(sound_model_handle_t model_handle,
+            sound_trigger_sound_model_type_t model_type,
+            recognition_callback_t recognition_callback, void *recognition_cookie,
+            struct sound_trigger_recognition_config *config) {
+    if (recognition_callback == NULL) {
+        ALOGI("%s No matching callback for handle %d", __func__, model_handle);
+        return;
     }
 
-    event->num_phrases = 1;
-    event->phrase_extras[0].confidence_level = 100;
-    event->phrase_extras[0].num_levels = 1;
-    event->phrase_extras[0].levels[0].level = 100;
-    event->phrase_extras[0].levels[0].user_id = 0;
-    // Signify that all the data is comming through streaming, not through the buffer.
-    event->common.capture_available = true;
-
-    event->common.audio_config = AUDIO_CONFIG_INITIALIZER;
-    event->common.audio_config.sample_rate = 16000;
-    event->common.audio_config.channel_mask = AUDIO_CHANNEL_IN_MONO;
-    event->common.audio_config.format = AUDIO_FORMAT_PCM_16_BIT;
-
-    return data;
+    if (model_type == SOUND_MODEL_TYPE_KEYPHRASE) {
+        struct sound_trigger_phrase_recognition_event *event;
+        event = (struct sound_trigger_phrase_recognition_event *)
+               sound_trigger_event_alloc(model_handle, model_type, config);
+        if (event) {
+            recognition_callback(&event->common, recognition_cookie);
+            free(event);
+        }
+    } else if (model_type == SOUND_MODEL_TYPE_GENERIC) {
+        struct sound_trigger_generic_recognition_event *event;
+        event = (struct sound_trigger_generic_recognition_event *)
+                sound_trigger_event_alloc(model_handle, model_type, config);
+        if (event) {
+            recognition_callback(&event->common, recognition_cookie);
+            free(event);
+        }
+    } else {
+        ALOGI("Unknown Sound Model Type, No Event to Send");
+    }
 }
 
 static void *callback_thread_loop(void *context) {
@@ -215,26 +253,26 @@
                     ALOGI("Received kill signal: stop listening to incoming server messages");
                     exit = true;
                 } else if (index < hw_properties.max_sound_models) {
-                    ALOGI("Going to send trigger for model #%d", index );
-                    if (stdev->model_context[index].recognition_callback != NULL) {
-                        sound_model_handle_t handle = stdev->model_context[index].loaded_sound_model;
-                        if (handle == 0) {
-                            ALOGW("This trigger is not loaded");
-                        } else {
-                            struct sound_trigger_phrase_recognition_event *event;
-                            event = (struct sound_trigger_phrase_recognition_event *)
-                                   sound_trigger_event_alloc(stdev, handle);
-                            if (event) {
-                               ALOGI("%s send callback model %d", __func__, index);
-                               stdev->model_context[index].recognition_callback(&event->common,
-                                                     stdev->model_context[index].recognition_cookie);
-                               free(event);
-                               stdev->model_context[index].recognition_callback = NULL;
-                            }
-                            exit = true;
+                    ALOGI("Going to send trigger for model index #%d", index );
+                    struct recognition_context *model_context = NULL;
+                    struct recognition_context *last_model_context = stdev->root_model_context;
+                    int model_index = 0;
+                    while(last_model_context) {
+                        if (model_index == index) {
+                            model_context = last_model_context;
+                            break;
                         }
+                        last_model_context = last_model_context->next;
+                        model_index++;
+                    }
+                    if (model_context) {
+                        send_recognition_event(model_context->model_handle,
+                                  model_context->model_type,
+                                  model_context->recognition_callback,
+                                  model_context->recognition_cookie,
+                                  model_context->config);
                     } else {
-                       ALOGI("%s No matching callback for %d", __func__, index);
+                        ALOGI("Sound Model Does Not Exist at this Index: %d", index);
                     }
                 } else {
                     ALOGI("Data is not recognized: %d", index);
@@ -302,29 +340,46 @@
         return -EINVAL;
     }
 
-    /* Find if there is space for this sound model */
-    unsigned int model_index;
-    bool found = false;
-    for(model_index = 0; model_index < hw_properties.max_sound_models; model_index++) {
-        if (stdev->model_context[model_index].loaded_sound_model == 0) {
-            found = true;
-            break;
-        }
-    }
-    if (found == false) {
-        ALOGW("Can't load model: reached max sound model limit");
+    struct recognition_context *model_context;
+    model_context = malloc(sizeof(struct recognition_context));
+    if(!model_context) {
+        ALOGW("Could not allocate recognition_context");
         pthread_mutex_unlock(&stdev->lock);
         return -ENOSYS;
     }
 
-    stdev->model_context[model_index].loaded_sound_model = generate_sound_model_id(dev);
-    *handle = stdev->model_context[model_index].loaded_sound_model;
+    // Add the new model context to the recognition_context linked list
+    if (stdev->root_model_context) {
+        // Find the tail
+        struct recognition_context *last_model_context = stdev->root_model_context;
+        int model_count = 0;
+        while(last_model_context->next) {
+            last_model_context = last_model_context->next;
+            model_count++;
+            if (model_count >= hw_properties.max_sound_models) {
+                ALOGW("Can't load model: reached max sound model limit");
+                free(model_context);
+                pthread_mutex_unlock(&stdev->lock);
+                return -ENOSYS;
+            }
+        }
+        last_model_context->next = model_context;
+    } else {
+        stdev->root_model_context = model_context;
+    }
+
+    model_context->model_handle = generate_sound_model_id(dev);
+    *handle = model_context->model_handle;
+    model_context->model_type = sound_model->type;
 
     char *data = (char *)sound_model + sound_model->data_offset;
     ALOGI("%s data size %d data %d - %d", __func__,
           sound_model->data_size, data[0], data[sound_model->data_size - 1]);
-    stdev->model_context[model_index].sound_model_callback = callback;
-    stdev->model_context[model_index].sound_model_cookie = cookie;
+    model_context->model_callback = callback;
+    model_context->model_cookie = cookie;
+    model_context->config = NULL;
+    model_context->recognition_callback = NULL;
+    model_context->recognition_cookie = NULL;
 
     pthread_mutex_unlock(&stdev->lock);
     return status;
@@ -337,35 +392,46 @@
     ALOGI("unload_sound_model");
     pthread_mutex_lock(&stdev->lock);
 
-    unsigned int i;
-    unsigned int model_index;
-    bool found = false;
-    bool other_callbacks_found = false;
-    for(i = 0; i < hw_properties.max_sound_models; i++) {
-        if (stdev->model_context[i].loaded_sound_model == handle) {
-            found = true;
-            model_index = i;
-            break;
-        } else if (stdev->model_context[i].recognition_callback != NULL) {
-            other_callbacks_found = true;
+
+    struct recognition_context *model_context = NULL;
+    struct recognition_context *previous_model_context = NULL;
+    if (stdev->root_model_context) {
+        struct recognition_context *last_model_context = stdev->root_model_context;
+        while(last_model_context) {
+            if (last_model_context->model_handle == handle) {
+                model_context = last_model_context;
+                break;
+            }
+            previous_model_context = last_model_context;
+            last_model_context = last_model_context->next;
         }
     }
-    if (found == false) {
-        ALOGW("Can't sound model %d in registered list", handle);
+    if (!model_context) {
+        ALOGW("Can't find sound model handle %d in registered list", handle);
         pthread_mutex_unlock(&stdev->lock);
         return -ENOSYS;
     }
 
-    stdev->model_context[i].loaded_sound_model = 0;
-    stdev->model_context[i].sound_model_callback = NULL;
-    stdev->model_context[i].sound_model_cookie = NULL;
-
-    free(stdev->model_context[i].config);
-    stdev->model_context[i].config = NULL;
-    stdev->model_context[i].recognition_callback = NULL;
-    stdev->model_context[i].recognition_cookie = NULL;
+    if(previous_model_context) {
+        previous_model_context->next = model_context->next;
+    } else {
+        stdev->root_model_context = model_context->next;
+    }
+    free(model_context->config);
+    free(model_context);
 
     /* If no more models running with callbacks, stop trigger thread */
+    bool other_callbacks_found = false;
+    if (stdev->root_model_context) {
+        struct recognition_context *last_model_context = stdev->root_model_context;
+        while(last_model_context) {
+            if (last_model_context->recognition_callback != NULL) {
+                other_callbacks_found = true;
+                break;
+            }
+            last_model_context = last_model_context->next;
+        }
+    }
     if (!other_callbacks_found) {
         send_loop_kill_signal();
         pthread_mutex_unlock(&stdev->lock);
@@ -385,32 +451,36 @@
     ALOGI("%s", __func__);
     struct stub_sound_trigger_device *stdev = (struct stub_sound_trigger_device *)dev;
     pthread_mutex_lock(&stdev->lock);
-    unsigned int i;
-    bool found = false;
-    for(i = 0; i < hw_properties.max_sound_models; i++) {
-        if (stdev->model_context[i].loaded_sound_model == handle) {
-            found = true;
-            break;
+
+    struct recognition_context *model_context = NULL;
+    if (stdev->root_model_context) {
+        struct recognition_context *last_model_context = stdev->root_model_context;
+        while(last_model_context) {
+            if (last_model_context->model_handle == handle) {
+                model_context = last_model_context;
+                break;
+            }
+            last_model_context = last_model_context->next;
         }
     }
-    if (found == false) {
-        ALOGW("Can't sound model %d in registered list", handle);
+    if (!model_context) {
+        ALOGW("Can't find sound model handle %d in registered list", handle);
         pthread_mutex_unlock(&stdev->lock);
         return -ENOSYS;
     }
 
-    free(stdev->model_context[i].config);
-    stdev->model_context[i].config = NULL;
+    free(model_context->config);
+    model_context->config = NULL;
     if (config) {
-        stdev->model_context[i].config = malloc(sizeof(*config));
-        if (!stdev->model_context[i].config) {
+        model_context->config = malloc(sizeof(*config));
+        if (!model_context->config) {
             pthread_mutex_unlock(&stdev->lock);
             return -ENOMEM;
         }
-        memcpy(stdev->model_context[i].config, config, sizeof(*config));
+        memcpy(model_context->config, config, sizeof(*config));
     }
-    stdev->model_context[i].recognition_callback = callback;
-    stdev->model_context[i].recognition_cookie = cookie;
+    model_context->recognition_callback = callback;
+    model_context->recognition_cookie = cookie;
 
     pthread_create(&stdev->callback_thread, (const pthread_attr_t *) NULL,
                         callback_thread_loop, stdev);
@@ -424,48 +494,56 @@
     ALOGI("%s", __func__);
     pthread_mutex_lock(&stdev->lock);
 
-    unsigned int i;
-    bool found = false;
-    for(i = 0; i < hw_properties.max_sound_models; i++) {
-        if (stdev->model_context[i].loaded_sound_model == handle) {
-            found = true;
-            break;
+    struct recognition_context *model_context = NULL;
+    bool other_callbacks_found = false;
+    if (stdev->root_model_context) {
+        struct recognition_context *last_model_context = stdev->root_model_context;
+        while(last_model_context) {
+            if (last_model_context->model_handle == handle) {
+                model_context = last_model_context;
+            } else if (last_model_context->recognition_callback != NULL) {
+                other_callbacks_found = true;
+            }
+            last_model_context = last_model_context->next;
         }
     }
-    if (found == false) {
-        ALOGW("Can't sound model %d in registered list", handle);
+    if (!model_context) {
+        ALOGW("Can't find sound model handle %d in registered list", handle);
         pthread_mutex_unlock(&stdev->lock);
         return -ENOSYS;
     }
 
-    free(stdev->model_context[i].config);
-    stdev->model_context[i].config = NULL;
-    stdev->model_context[i].recognition_callback = NULL;
-    stdev->model_context[i].recognition_cookie = NULL;
+    free(model_context->config);
+    model_context->config = NULL;
+    model_context->recognition_callback = NULL;
+    model_context->recognition_cookie = NULL;
 
-    send_loop_kill_signal();
-    pthread_mutex_unlock(&stdev->lock);
-    pthread_join(stdev->callback_thread, (void **) NULL);
+    /* If no more models running with callbacks, stop trigger thread */
+    if (!other_callbacks_found) {
+        send_loop_kill_signal();
+        pthread_mutex_unlock(&stdev->lock);
+        pthread_join(stdev->callback_thread, (void **)NULL);
+    } else {
+        pthread_mutex_unlock(&stdev->lock);
+    }
+
     return 0;
 }
 
 __attribute__ ((visibility ("default")))
-int sound_trigger_open_for_streaming()
-{
+int sound_trigger_open_for_streaming() {
     int ret = 0;
     return ret;
 }
 
 __attribute__ ((visibility ("default")))
-size_t sound_trigger_read_samples(int audio_handle, void *buffer, size_t  buffer_len)
-{
+size_t sound_trigger_read_samples(int audio_handle, void *buffer, size_t  buffer_len) {
     size_t ret = 0;
     return ret;
 }
 
 __attribute__ ((visibility ("default")))
-int sound_trigger_close_for_streaming(int audio_handle __unused)
-{
+int sound_trigger_close_for_streaming(int audio_handle __unused) {
     return 0;
 }
 
@@ -486,21 +564,7 @@
     if (!stdev)
         return -ENOMEM;
 
-    if (MAX_MAX_SOUND_MODELS < hw_properties.max_sound_models) {
-        ALOGW("max_sound_models is greater than the allowed %d", MAX_MAX_SOUND_MODELS);
-        return -EINVAL;
-    }
-
     stdev->next_sound_model_id = 1;
-    unsigned int i;
-    for(i = 0; i < hw_properties.max_sound_models; i++) {
-        stdev->model_context[i].loaded_sound_model = 0;
-        stdev->model_context[i].sound_model_callback = NULL;
-        stdev->model_context[i].sound_model_cookie = NULL;
-        stdev->model_context[i].config = NULL;
-        stdev->model_context[i].recognition_callback = NULL;
-        stdev->model_context[i].recognition_cookie = NULL;
-    }
 
     stdev->device.common.tag = HARDWARE_DEVICE_TAG;
     stdev->device.common.version = SOUND_TRIGGER_DEVICE_API_VERSION_1_0;
@@ -534,3 +598,4 @@
         .methods = &hal_module_methods,
     },
 };
+