BBeOS/docs/phases/PHASE_5_TELEPHONY.md

Phase 5: Telephony & Messaging Stack Development

🎯 Objectives

Develop a complete telephony and messaging system that provides calling, SMS, and data connectivity functionality for the BlackBerry Classic (Q20).

📋 Detailed Tasks

5.1 Modem Integration

5.1.1 Modem Hardware Analysis

Qualcomm MDM9615 Specifications:

• Technology: LTE Cat 3, HSPA+, CDMA
• Interface: QMI over USB or HSIC
• Firmware: Proprietary binary blob
• Power Management: Integrated power control
• Security: Hardware security modules

Modem Interface Options:

1. QMI (Qualcomm MSM Interface): Primary interface
2. AT Commands: Standard modem commands
3. HSIC (High-Speed Inter-Chip): Direct connection
4. USB: Standard USB interface

Hardware Integration:

// Modem device structure
struct q20_modem {
    struct device *dev;
    struct usb_device *usb_dev;
    struct qmi_device *qmi_dev;
    
    // Modem state
    enum modem_state state;
    bool powered;
    bool registered;
    bool data_connected;
    
    // Network information
    struct network_info network;
    struct signal_info signal;
    struct sim_info sim;
    
    // Power management
    struct regulator *vdd;
    struct gpio_desc *reset_gpio;
    struct gpio_desc *power_gpio;
    
    // Communication
    struct workqueue_struct *workqueue;
    struct work_struct init_work;
    struct work_struct power_work;
    
    // Callbacks
    void (*call_state_cb)(struct call_info *call);
    void (*sms_received_cb)(struct sms_info *sms);
    void (*network_state_cb)(struct network_info *network);
};

// Network information
struct network_info {
    char mcc[4];
    char mnc[4];
    char operator_name[64];
    enum network_type type;
    int signal_strength;
    bool roaming;
};

// Signal information
struct signal_info {
    int rssi;
    int rsrp;
    int rsrq;
    int sinr;
    enum signal_quality quality;
};

5.1.2 QMI Interface Implementation

QMI Protocol Stack:

// QMI device structure
struct qmi_device {
    struct usb_device *usb_dev;
    struct urb *urb;
    struct mutex mutex;
    
    // QMI state
    u16 transaction_id;
    u8 service_id;
    bool connected;
    
    // Message handling
    struct list_head pending_requests;
    struct work_struct message_work;
    
    // Service handlers
    struct qmi_service *wds_service;  // Wireless Data Service
    struct qmi_service *dms_service;  // Device Management Service
    struct qmi_service *nas_service;  // Network Access Service
    struct qmi_service *wms_service;  // Wireless Messaging Service
    struct qmi_service *voice_service; // Voice Service
};

// QMI message structure
struct qmi_message {
    struct list_head list;
    u16 transaction_id;
    u8 service_id;
    u8 message_id;
    u16 message_length;
    u8 *message_data;
    void (*callback)(struct qmi_message *msg, void *data);
    void *callback_data;
};

// QMI service implementation
struct qmi_service {
    struct qmi_device *qmi_dev;
    u8 service_id;
    char service_name[32];
    
    // Service operations
    int (*init)(struct qmi_service *service);
    void (*deinit)(struct qmi_service *service);
    int (*send_message)(struct qmi_service *service, u8 message_id,
                       void *data, size_t data_len,
                       void (*callback)(struct qmi_message *msg, void *data),
                       void *callback_data);
    void (*handle_message)(struct qmi_service *service, struct qmi_message *msg);
};

// WDS (Wireless Data Service) implementation
static int qmi_wds_init(struct qmi_service *service)
{
    struct qmi_wds_service *wds = container_of(service, struct qmi_wds_service, service);
    
    // Initialize WDS service
    wds->service.service_id = QMI_WDS_SERVICE_ID;
    strcpy(wds->service.service_name, "WDS");
    
    // Register message handlers
    wds->service.handle_message = qmi_wds_handle_message;
    
    return 0;
}

static int qmi_wds_start_network(struct qmi_service *service, const char *apn)
{
    struct qmi_wds_start_network_req req;
    struct qmi_message *msg;
    
    // Prepare request
    memset(&req, 0, sizeof(req));
    req.profile_index = 1;
    strncpy(req.apn, apn, sizeof(req.apn) - 1);
    
    // Send message
    msg = qmi_alloc_message(service->qmi_dev, QMI_WDS_START_NETWORK_MSG_ID,
                           &req, sizeof(req));
    if (!msg)
        return -ENOMEM;
    
    return qmi_send_message(service->qmi_dev, msg);
}

5.1.3 Modem Power Management

Power Management Implementation:

// Modem power management
static int q20_modem_power_on(struct q20_modem *modem)
{
    int ret;
    
    // Enable power supply
    ret = regulator_enable(modem->vdd);
    if (ret)
        return ret;
    
    // Assert reset
    gpiod_set_value(modem->reset_gpio, 0);
    msleep(10);
    
    // De-assert reset
    gpiod_set_value(modem->reset_gpio, 1);
    msleep(100);
    
    // Assert power
    gpiod_set_value(modem->power_gpio, 1);
    msleep(1000);
    
    // Initialize QMI interface
    ret = qmi_device_init(modem->qmi_dev);
    if (ret)
        goto power_off;
    
    // Start initialization work
    queue_work(modem->workqueue, &modem->init_work);
    
    modem->powered = true;
    return 0;
    
power_off:
    q20_modem_power_off(modem);
    return ret;
}

static int q20_modem_power_off(struct q20_modem *modem)
{
    // De-assert power
    gpiod_set_value(modem->power_gpio, 0);
    msleep(100);
    
    // Assert reset
    gpiod_set_value(modem->reset_gpio, 0);
    
    // Disable power supply
    regulator_disable(modem->vdd);
    
    modem->powered = false;
    modem->registered = false;
    modem->data_connected = false;
    
    return 0;
}

// Modem initialization work
static void q20_modem_init_work(struct work_struct *work)
{
    struct q20_modem *modem = container_of(work, struct q20_modem, init_work);
    int ret;
    
    // Initialize QMI services
    ret = qmi_wds_init(&modem->qmi_dev->wds_service);
    if (ret)
        goto init_failed;
    
    ret = qmi_dms_init(&modem->qmi_dev->dms_service);
    if (ret)
        goto init_failed;
    
    ret = qmi_nas_init(&modem->qmi_dev->nas_service);
    if (ret)
        goto init_failed;
    
    ret = qmi_wms_init(&modem->qmi_dev->wms_service);
    if (ret)
        goto init_failed;
    
    ret = qmi_voice_init(&modem->qmi_dev->voice_service);
    if (ret)
        goto init_failed;
    
    // Get device information
    ret = qmi_dms_get_device_info(&modem->qmi_dev->dms_service);
    if (ret)
        goto init_failed;
    
    // Get SIM information
    ret = qmi_dms_get_sim_info(&modem->qmi_dev->dms_service);
    if (ret)
        goto init_failed;
    
    // Register for network events
    ret = qmi_nas_register_for_events(&modem->qmi_dev->nas_service);
    if (ret)
        goto init_failed;
    
    // Register for SMS events
    ret = qmi_wms_register_for_events(&modem->qmi_dev->wms_service);
    if (ret)
        goto init_failed;
    
    // Register for voice events
    ret = qmi_voice_register_for_events(&modem->qmi_dev->voice_service);
    if (ret)
        goto init_failed;
    
    modem->state = MODEM_STATE_READY;
    return;
    
init_failed:
    dev_err(modem->dev, "Modem initialization failed: %d\n", ret);
    q20_modem_power_off(modem);
}

5.2 Voice Call System

5.2.1 Voice Service Implementation

Voice Call Management:

// Voice call structure
struct q20_call {
    struct list_head list;
    u8 call_id;
    enum call_state state;
    enum call_type type;
    
    // Call information
    char number[32];
    char name[64];
    u32 duration;
    struct timespec start_time;
    
    // Audio management
    bool audio_connected;
    bool muted;
    bool speaker_on;
    
    // Callbacks
    void (*state_changed_cb)(struct q20_call *call);
    void (*audio_state_cb)(struct q20_call *call);
};

// Voice service implementation
struct q20_voice_service {
    struct qmi_service service;
    struct q20_modem *modem;
    
    // Call management
    struct list_head active_calls;
    struct q20_call *current_call;
    u8 next_call_id;
    
    // Audio management
    struct q20_audio_manager *audio_mgr;
    
    // Callbacks
    void (*call_state_changed_cb)(struct q20_call *call);
    void (*incoming_call_cb)(struct q20_call *call);
    void (*call_ended_cb)(struct q20_call *call);
};

// Voice service operations
static int q20_voice_dial(struct q20_voice_service *voice, const char *number)
{
    struct qmi_voice_dial_req req;
    struct qmi_message *msg;
    struct q20_call *call;
    int ret;
    
    // Create call structure
    call = kzalloc(sizeof(*call), GFP_KERNEL);
    if (!call)
        return -ENOMEM;
    
    call->call_id = voice->next_call_id++;
    call->state = CALL_STATE_DIALING;
    call->type = CALL_TYPE_VOICE;
    strncpy(call->number, number, sizeof(call->number) - 1);
    
    // Add to active calls
    list_add_tail(&call->list, &voice->active_calls);
    voice->current_call = call;
    
    // Prepare dial request
    memset(&req, 0, sizeof(req));
    req.call_id = call->call_id;
    strncpy(req.number, number, sizeof(req.number) - 1);
    req.call_type = QMI_VOICE_CALL_TYPE_VOICE;
    
    // Send dial request
    msg = qmi_alloc_message(&voice->service, QMI_VOICE_DIAL_MSG_ID,
                           &req, sizeof(req));
    if (!msg) {
        ret = -ENOMEM;
        goto dial_failed;
    }
    
    msg->callback = q20_voice_dial_callback;
    msg->callback_data = call;
    
    ret = qmi_send_message(voice->service.qmi_dev, msg);
    if (ret)
        goto dial_failed;
    
    // Start call timer
    call->start_time = current_kernel_time();
    
    return 0;
    
dial_failed:
    list_del(&call->list);
    kfree(call);
    return ret;
}

static int q20_voice_answer(struct q20_voice_service *voice, struct q20_call *call)
{
    struct qmi_voice_answer_req req;
    struct qmi_message *msg;
    int ret;
    
    if (!call || call->state != CALL_STATE_INCOMING)
        return -EINVAL;
    
    // Prepare answer request
    memset(&req, 0, sizeof(req));
    req.call_id = call->call_id;
    
    // Send answer request
    msg = qmi_alloc_message(&voice->service, QMI_VOICE_ANSWER_MSG_ID,
                           &req, sizeof(req));
    if (!msg)
        return -ENOMEM;
    
    msg->callback = q20_voice_answer_callback;
    msg->callback_data = call;
    
    ret = qmi_send_message(voice->service.qmi_dev, msg);
    if (ret)
        return ret;
    
    call->state = CALL_STATE_ANSWERING;
    return 0;
}

static int q20_voice_end_call(struct q20_voice_service *voice, struct q20_call *call)
{
    struct qmi_voice_end_call_req req;
    struct qmi_message *msg;
    int ret;
    
    if (!call)
        return -EINVAL;
    
    // Prepare end call request
    memset(&req, 0, sizeof(req));
    req.call_id = call->call_id;
    
    // Send end call request
    msg = qmi_alloc_message(&voice->service, QMI_VOICE_END_CALL_MSG_ID,
                           &req, sizeof(req));
    if (!msg)
        return -ENOMEM;
    
    msg->callback = q20_voice_end_call_callback;
    msg->callback_data = call;
    
    ret = qmi_send_message(voice->service.qmi_dev, msg);
    if (ret)
        return ret;
    
    call->state = CALL_STATE_ENDING;
    return 0;
}

5.2.2 Audio Management

Call Audio System:

// Audio manager for calls
struct q20_audio_manager {
    struct q20_modem *modem;
    
    // Audio state
    bool call_audio_active;
    bool speaker_on;
    bool muted;
    
    // Audio routing
    enum audio_route current_route;
    struct q20_audio_route *routes;
    int num_routes;
    
    // Audio control
    struct q20_audio_control *control;
};

// Audio routing implementation
static int q20_audio_route_call_audio(struct q20_audio_manager *audio_mgr,
                                     enum audio_route route)
{
    struct q20_audio_route *audio_route;
    int ret;
    
    // Find audio route
    audio_route = q20_audio_find_route(audio_mgr, route);
    if (!audio_route)
        return -EINVAL;
    
    // Configure audio path
    ret = q20_audio_configure_path(audio_mgr, audio_route);
    if (ret)
        return ret;
    
    // Update state
    audio_mgr->current_route = route;
    audio_mgr->call_audio_active = true;
    
    return 0;
}

static int q20_audio_mute_call(struct q20_audio_manager *audio_mgr, bool mute)
{
    int ret;
    
    if (mute == audio_mgr->muted)
        return 0;
    
    // Configure mute
    ret = q20_audio_configure_mute(audio_mgr, mute);
    if (ret)
        return ret;
    
    audio_mgr->muted = mute;
    return 0;
}

static int q20_audio_toggle_speaker(struct q20_audio_manager *audio_mgr)
{
    enum audio_route new_route;
    int ret;
    
    if (audio_mgr->speaker_on) {
        new_route = AUDIO_ROUTE_EARPIECE;
    } else {
        new_route = AUDIO_ROUTE_SPEAKER;
    }
    
    ret = q20_audio_route_call_audio(audio_mgr, new_route);
    if (ret)
        return ret;
    
    audio_mgr->speaker_on = (new_route == AUDIO_ROUTE_SPEAKER);
    return 0;
}

5.3 SMS System

5.3.1 SMS Service Implementation

SMS Management:

// SMS message structure
struct q20_sms {
    struct list_head list;
    u32 message_id;
    enum sms_type type;
    enum sms_state state;
    
    // Message content
    char number[32];
    char text[160];
    struct timespec timestamp;
    
    // Message metadata
    bool read;
    bool sent;
    u8 parts;
    u8 part_number;
};

// SMS service implementation
struct q20_sms_service {
    struct qmi_service service;
    struct q20_modem *modem;
    
    // Message storage
    struct list_head messages;
    struct q20_sms_storage *storage;
    
    // Message handling
    u32 next_message_id;
    struct work_struct message_work;
    
    // Callbacks
    void (*message_received_cb)(struct q20_sms *sms);
    void (*message_sent_cb)(struct q20_sms *sms);
    void (*message_failed_cb)(struct q20_sms *sms);
};

// SMS operations
static int q20_sms_send_message(struct q20_sms_service *sms_service,
                               const char *number, const char *text)
{
    struct qmi_wms_send_sms_req req;
    struct qmi_message *msg;
    struct q20_sms *sms;
    int ret;
    
    // Create SMS structure
    sms = kzalloc(sizeof(*sms), GFP_KERNEL);
    if (!sms)
        return -ENOMEM;
    
    sms->message_id = sms_service->next_message_id++;
    sms->type = SMS_TYPE_OUTGOING;
    sms->state = SMS_STATE_SENDING;
    strncpy(sms->number, number, sizeof(sms->number) - 1);
    strncpy(sms->text, text, sizeof(sms->text) - 1);
    sms->timestamp = current_kernel_time();
    
    // Add to message list
    list_add_tail(&sms->list, &sms_service->messages);
    
    // Store message
    ret = q20_sms_store_message(sms_service->storage, sms);
    if (ret)
        goto send_failed;
    
    // Prepare send request
    memset(&req, 0, sizeof(req));
    req.message_id = sms->message_id;
    strncpy(req.number, number, sizeof(req.number) - 1);
    strncpy(req.text, text, sizeof(req.text) - 1);
    req.message_format = QMI_WMS_MESSAGE_FORMAT_GSM;
    
    // Send SMS request
    msg = qmi_alloc_message(&sms_service->service, QMI_WMS_SEND_SMS_MSG_ID,
                           &req, sizeof(req));
    if (!msg) {
        ret = -ENOMEM;
        goto send_failed;
    }
    
    msg->callback = q20_sms_send_callback;
    msg->callback_data = sms;
    
    ret = qmi_send_message(sms_service->service.qmi_dev, msg);
    if (ret)
        goto send_failed;
    
    return 0;
    
send_failed:
    list_del(&sms->list);
    kfree(sms);
    return ret;
}

static int q20_sms_delete_message(struct q20_sms_service *sms_service,
                                 struct q20_sms *sms)
{
    int ret;
    
    if (!sms)
        return -EINVAL;
    
    // Remove from storage
    ret = q20_sms_remove_message(sms_service->storage, sms);
    if (ret)
        return ret;
    
    // Remove from list
    list_del(&sms->list);
    kfree(sms);
    
    return 0;
}

// SMS callback handlers
static void q20_sms_send_callback(struct qmi_message *msg, void *data)
{
    struct q20_sms *sms = data;
    struct qmi_wms_send_sms_resp *resp = msg->message_data;
    
    if (resp->result == QMI_RESULT_SUCCESS) {
        sms->state = SMS_STATE_SENT;
        sms->sent = true;
        
        if (sms->service->message_sent_cb)
            sms->service->message_sent_cb(sms);
    } else {
        sms->state = SMS_STATE_FAILED;
        
        if (sms->service->message_failed_cb)
            sms->service->message_failed_cb(sms);
    }
}

static void q20_sms_received_callback(struct qmi_message *msg, void *data)
{
    struct q20_sms_service *sms_service = data;
    struct qmi_wms_message_received_ind *ind = msg->message_data;
    struct q20_sms *sms;
    
    // Create SMS structure
    sms = kzalloc(sizeof(*sms), GFP_KERNEL);
    if (!sms)
        return;
    
    sms->message_id = sms_service->next_message_id++;
    sms->type = SMS_TYPE_INCOMING;
    sms->state = SMS_STATE_RECEIVED;
    strncpy(sms->number, ind->number, sizeof(sms->number) - 1);
    strncpy(sms->text, ind->text, sizeof(sms->text) - 1);
    sms->timestamp = current_kernel_time();
    
    // Add to message list
    list_add_tail(&sms->list, &sms_service->messages);
    
    // Store message
    q20_sms_store_message(sms_service->storage, sms);
    
    // Notify application
    if (sms_service->message_received_cb)
        sms_service->message_received_cb(sms);
}

5.3.2 SMS Storage System

Message Storage:

// SMS storage interface
struct q20_sms_storage {
    struct device *dev;
    
    // Storage operations
    int (*store_message)(struct q20_sms_storage *storage, struct q20_sms *sms);
    int (*load_messages)(struct q20_sms_storage *storage, struct list_head *messages);
    int (*remove_message)(struct q20_sms_storage *storage, struct q20_sms *sms);
    int (*clear_messages)(struct q20_sms_storage *storage);
    
    // Storage backend
    void *private_data;
};

// SQLite storage implementation
struct q20_sms_sqlite_storage {
    struct q20_sms_storage storage;
    sqlite3 *db;
    char *db_path;
};

static int q20_sms_sqlite_store_message(struct q20_sms_storage *storage,
                                       struct q20_sms *sms)
{
    struct q20_sms_sqlite_storage *sqlite_storage = 
        container_of(storage, struct q20_sms_sqlite_storage, storage);
    sqlite3_stmt *stmt;
    int ret;
    
    const char *sql = "INSERT INTO messages (id, type, number, text, timestamp, read, sent) "
                      "VALUES (?, ?, ?, ?, ?, ?, ?)";
    
    ret = sqlite3_prepare_v2(sqlite_storage->db, sql, -1, &stmt, NULL);
    if (ret != SQLITE_OK)
        return -EIO;
    
    sqlite3_bind_int(stmt, 1, sms->message_id);
    sqlite3_bind_int(stmt, 2, sms->type);
    sqlite3_bind_text(stmt, 3, sms->number, -1, SQLITE_STATIC);
    sqlite3_bind_text(stmt, 4, sms->text, -1, SQLITE_STATIC);
    sqlite3_bind_int64(stmt, 5, sms->timestamp.tv_sec);
    sqlite3_bind_int(stmt, 6, sms->read);
    sqlite3_bind_int(stmt, 7, sms->sent);
    
    ret = sqlite3_step(stmt);
    sqlite3_finalize(stmt);
    
    return (ret == SQLITE_DONE) ? 0 : -EIO;
}

static int q20_sms_sqlite_load_messages(struct q20_sms_storage *storage,
                                       struct list_head *messages)
{
    struct q20_sms_sqlite_storage *sqlite_storage = 
        container_of(storage, struct q20_sms_sqlite_storage, storage);
    sqlite3_stmt *stmt;
    int ret;
    
    const char *sql = "SELECT id, type, number, text, timestamp, read, sent "
                      "FROM messages ORDER BY timestamp DESC";
    
    ret = sqlite3_prepare_v2(sqlite_storage->db, sql, -1, &stmt, NULL);
    if (ret != SQLITE_OK)
        return -EIO;
    
    while (sqlite3_step(stmt) == SQLITE_ROW) {
        struct q20_sms *sms = kzalloc(sizeof(*sms), GFP_KERNEL);
        if (!sms)
            continue;
        
        sms->message_id = sqlite3_column_int(stmt, 0);
        sms->type = sqlite3_column_int(stmt, 1);
        strncpy(sms->number, (char*)sqlite3_column_text(stmt, 2), sizeof(sms->number) - 1);
        strncpy(sms->text, (char*)sqlite3_column_text(stmt, 3), sizeof(sms->text) - 1);
        sms->timestamp.tv_sec = sqlite3_column_int64(stmt, 4);
        sms->read = sqlite3_column_int(stmt, 5);
        sms->sent = sqlite3_column_int(stmt, 6);
        
        list_add_tail(&sms->list, messages);
    }
    
    sqlite3_finalize(stmt);
    return 0;
}

5.4 Data Connectivity

5.4.1 Data Service Implementation

Data Connection Management:

// Data connection structure
struct q20_data_connection {
    struct q20_modem *modem;
    
    // Connection state
    bool connected;
    enum data_technology technology;
    char apn[64];
    
    // Network interface
    struct net_device *netdev;
    struct in_addr local_ip;
    struct in_addr gateway_ip;
    struct in_addr dns1_ip;
    struct in_addr dns2_ip;
    
    // Statistics
    u64 bytes_rx;
    u64 bytes_tx;
    u32 packets_rx;
    u32 packets_tx;
    
    // Callbacks
    void (*connected_cb)(struct q20_data_connection *conn);
    void (*disconnected_cb)(struct q20_data_connection *conn);
    void (*error_cb)(struct q20_data_connection *conn, int error);
};

// Data service operations
static int q20_data_connect(struct q20_data_connection *conn, const char *apn)
{
    struct qmi_wds_start_network_req req;
    struct qmi_message *msg;
    int ret;
    
    if (conn->connected)
        return -EALREADY;
    
    // Prepare connection request
    memset(&req, 0, sizeof(req));
    req.profile_index = 1;
    strncpy(req.apn, apn, sizeof(req.apn) - 1);
    req.auth_type = QMI_WDS_AUTH_TYPE_NONE;
    
    // Send start network request
    msg = qmi_alloc_message(&conn->modem->qmi_dev->wds_service,
                           QMI_WDS_START_NETWORK_MSG_ID,
                           &req, sizeof(req));
    if (!msg)
        return -ENOMEM;
    
    msg->callback = q20_data_connect_callback;
    msg->callback_data = conn;
    
    ret = qmi_send_message(conn->modem->qmi_dev, msg);
    if (ret)
        return ret;
    
    strncpy(conn->apn, apn, sizeof(conn->apn) - 1);
    return 0;
}

static int q20_data_disconnect(struct q20_data_connection *conn)
{
    struct qmi_wds_stop_network_req req;
    struct qmi_message *msg;
    int ret;
    
    if (!conn->connected)
        return -ENOTCONN;
    
    // Prepare disconnect request
    memset(&req, 0, sizeof(req));
    req.profile_index = 1;
    
    // Send stop network request
    msg = qmi_alloc_message(&conn->modem->qmi_dev->wds_service,
                           QMI_WDS_STOP_NETWORK_MSG_ID,
                           &req, sizeof(req));
    if (!msg)
        return -ENOMEM;
    
    msg->callback = q20_data_disconnect_callback;
    msg->callback_data = conn;
    
    ret = qmi_send_message(conn->modem->qmi_dev, msg);
    if (ret)
        return ret;
    
    return 0;
}

// Data connection callbacks
static void q20_data_connect_callback(struct qmi_message *msg, void *data)
{
    struct q20_data_connection *conn = data;
    struct qmi_wds_start_network_resp *resp = msg->message_data;
    
    if (resp->result == QMI_RESULT_SUCCESS) {
        conn->connected = true;
        conn->technology = resp->technology;
        
        // Configure network interface
        q20_data_configure_interface(conn);
        
        if (conn->connected_cb)
            conn->connected_cb(conn);
    } else {
        if (conn->error_cb)
            conn->error_cb(conn, -EIO);
    }
}

static void q20_data_disconnect_callback(struct qmi_message *msg, void *data)
{
    struct q20_data_connection *conn = data;
    struct qmi_wds_stop_network_resp *resp = msg->message_data;
    
    if (resp->result == QMI_RESULT_SUCCESS) {
        conn->connected = false;
        
        // Clean up network interface
        q20_data_cleanup_interface(conn);
        
        if (conn->disconnected_cb)
            conn->disconnected_cb(conn);
    }
}

📊 Deliverables

5.5 Complete Telephony Stack

Requirements:

• Functional modem integration
• Voice call system working
• SMS messaging system
• Data connectivity
• Network management

5.6 Telephony Applications

Components:

• Phone dialer application
• SMS messaging application
• Contacts management
• Call history
• Network settings

5.7 Integration Layer

Features:

• Modem abstraction layer
• Service management
• Event handling
• Error recovery
• Power management

⏱️ Timeline

Week 1-2: Modem integration Week 3-4: Voice call system Week 5-6: SMS system Week 7-8: Data connectivity Week 9-10: Network management Week 11-12: Testing and integration

Total Duration: 12 weeks (3 months)

🎯 Success Criteria

Phase 5 is successful when:

1. Complete telephony stack is functional
2. Voice calls work reliably
3. SMS messaging is operational
4. Data connectivity is stable
5. Network management is complete

🚨 Risk Mitigation

High-Risk Scenarios:

• Modem firmware issues → Extract and analyze firmware blobs
• QMI protocol complexity → Implement comprehensive testing
• Audio routing problems → Develop fallback audio paths
• Network connectivity issues → Implement robust error handling
• SMS storage problems → Use reliable storage backend