xref: /btstack/src/hci.c (revision 89db417b225cddfa845d0ad9d5599be5f37b9b6f)

/*
 * Copyright (C) 2009 by Matthias Ringwald
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions
 * are met:
 *
 * 1. Redistributions of source code must retain the above copyright
 *    notice, this list of conditions and the following disclaimer.
 * 2. Redistributions in binary form must reproduce the above copyright
 *    notice, this list of conditions and the following disclaimer in the
 *    documentation and/or other materials provided with the distribution.
 * 3. Neither the name of the copyright holders nor the names of
 *    contributors may be used to endorse or promote products derived
 *    from this software without specific prior written permission.
 *
 * THIS SOFTWARE IS PROVIDED BY MATTHIAS RINGWALD AND CONTRIBUTORS
 * ``AS IS'' AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
 * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS
 * FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL MATTHIAS
 * RINGWALD OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT,
 * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING,
 * BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS
 * OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED
 * AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY,
 * OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF
 * THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
 * SUCH DAMAGE.
 *
 */

/*
 *  hci.c
 *
 *  Created by Matthias Ringwald on 4/29/09.
 *
 */

#include "hci.h"

#include <unistd.h>
#include <stdarg.h>
#include <string.h>
#include <stdio.h>

#include "debug.h"
#include "hci_dump.h"

#include "../include/btstack/hci_cmds.h"
#include "../include/btstack/version.h"

// temp
#include "l2cap.h"

#define HCI_CONNECTION_TIMEOUT_MS 10000

// the STACK is here
static hci_stack_t       hci_stack;

/**
 * get connection for a given handle
 *
 * @return connection OR NULL, if not found
 */
hci_connection_t * connection_for_handle(hci_con_handle_t con_handle){
    linked_item_t *it;
    for (it = (linked_item_t *) hci_stack.connections; it ; it = it->next){
        if ( ((hci_connection_t *) it)->con_handle == con_handle){
            return (hci_connection_t *) it;
        }
    }
    return NULL;
}

static void hci_connection_timeout_handler(timer_source_t *timer){
    hci_connection_t * connection = linked_item_get_user(&timer->item);
    struct timeval tv;
    gettimeofday(&tv, NULL);
    if (tv.tv_sec >= connection->timestamp.tv_sec + HCI_CONNECTION_TIMEOUT_MS/1000) {
        // connections might be timed out
        hci_emit_l2cap_check_timeout(connection);
        run_loop_set_timer(timer, HCI_CONNECTION_TIMEOUT_MS);
    } else {
        // next timeout check at
        timer->timeout.tv_sec = connection->timestamp.tv_sec + HCI_CONNECTION_TIMEOUT_MS/1000;
    }
    run_loop_add_timer(timer);
}

static void hci_connection_timestamp(hci_connection_t *connection){
    gettimeofday(&connection->timestamp, NULL);
}

/**
 * create connection for given address
 *
 * @return connection OR NULL, if not found
 */
static hci_connection_t * create_connection_for_addr(bd_addr_t addr){
    hci_connection_t * conn = malloc( sizeof(hci_connection_t) );
    if (!conn) return NULL;
    BD_ADDR_COPY(conn->address, addr);
    conn->con_handle = 0xffff;
    conn->authentication_flags = 0;
    linked_item_set_user(&conn->timeout.item, conn);
    conn->timeout.process = hci_connection_timeout_handler;
    hci_connection_timestamp(conn);
    conn->acl_recombination_length = 0;
    conn->acl_recombination_pos = 0;
    conn->num_acl_packets_sent = 0;
    linked_list_add(&hci_stack.connections, (linked_item_t *) conn);
    return conn;
}

/**
 * get connection for given address
 *
 * @return connection OR NULL, if not found
 */
static hci_connection_t * connection_for_address(bd_addr_t address){
    linked_item_t *it;
    for (it = (linked_item_t *) hci_stack.connections; it ; it = it->next){
        if ( ! BD_ADDR_CMP( ((hci_connection_t *) it)->address, address) ){
            return (hci_connection_t *) it;
        }
    }
    return NULL;
}

/**
 * add authentication flags and reset timer
 */
static void hci_add_connection_flags_for_flipped_bd_addr(uint8_t *bd_addr, hci_authentication_flags_t flags){
    bd_addr_t addr;
    bt_flip_addr(addr, *(bd_addr_t *) bd_addr);
    hci_connection_t * conn = connection_for_address(addr);
    if (conn) {
        conn->authentication_flags |= flags;
        hci_connection_timestamp(conn);
    }
}

int  hci_authentication_active_for_handle(hci_con_handle_t handle){
    hci_connection_t * conn = connection_for_handle(handle);
    if (!conn) return 0;
    if (!conn->authentication_flags) return 0;
    if (conn->authentication_flags & SENT_LINK_KEY_REPLY) return 0;
    if (conn->authentication_flags & RECV_LINK_KEY_NOTIFICATION) return 0;
    return 1;
}

void hci_drop_link_key_for_bd_addr(bd_addr_t *addr){
    if (hci_stack.remote_device_db) {
        hci_stack.remote_device_db->delete_link_key(addr);
    }
}


/**
 * count connections
 */
static int nr_hci_connections(){
    int count = 0;
    linked_item_t *it;
    for (it = (linked_item_t *) hci_stack.connections; it ; it = it->next, count++);
    return count;
}

/**
 * Dummy handler called by HCI
 */
static void dummy_handler(uint8_t packet_type, uint8_t *packet, uint16_t size){
}

uint8_t hci_number_outgoing_packets(hci_con_handle_t handle){
    hci_connection_t * connection = connection_for_handle(handle);
    if (!connection) {
        log_err("hci_number_outgoing_packets connectino for handle %u does not exist!\n", handle);
        return 0;
    }
    return connection->num_acl_packets_sent;
}

uint8_t hci_number_free_acl_slots(){
    uint8_t free_slots = hci_stack.total_num_acl_packets;
    linked_item_t *it;
    for (it = (linked_item_t *) hci_stack.connections; it ; it = it->next){
        hci_connection_t * connection = (hci_connection_t *) it;
        if (free_slots < connection->num_acl_packets_sent) {
            log_err("hci_number_free_acl_slots: sum of outgoing packets > total acl packets!\n");
            return 0;
        }
        free_slots -= connection->num_acl_packets_sent;
    }
    return free_slots;
}

uint16_t hci_max_acl_data_packet_length(){
    return hci_stack.acl_data_packet_length;
}

int hci_ready_to_send(hci_con_handle_t handle){
    return hci_number_free_acl_slots() && hci_number_outgoing_packets(handle) < 2;
}

int hci_send_acl_packet(uint8_t *packet, int size){

    // check for free places on BT module
    if (!hci_number_free_acl_slots()) return -1;

    hci_con_handle_t con_handle = READ_ACL_CONNECTION_HANDLE(packet);
    hci_connection_t *connection = connection_for_handle( con_handle);
    if (!connection) return 0;
    hci_connection_timestamp(connection);

    // count packet
    connection->num_acl_packets_sent++;
    // log_dbg("hci_send_acl_packet - handle %u, sent %u\n", connection->con_handle, connection->num_acl_packets_sent);

    // send packet - ignore errors
    hci_stack.hci_transport->send_packet(HCI_ACL_DATA_PACKET, packet, size);

    return 0;
}

static void acl_handler(uint8_t *packet, int size){

    // get info
    hci_con_handle_t con_handle = READ_ACL_CONNECTION_HANDLE(packet);
    hci_connection_t *conn      = connection_for_handle(con_handle);
    uint8_t  acl_flags          = READ_ACL_FLAGS(packet);
    uint16_t acl_length         = READ_ACL_LENGTH(packet);

    // ignore non-registered handle
    if (!conn){
        log_err( "hci.c: acl_handler called with non-registered handle %u!\n" , con_handle);
        return;
    }

    // update idle timestamp
    hci_connection_timestamp(conn);

    // handle different packet types
    switch (acl_flags & 0x03) {

        case 0x01: // continuation fragment

            // sanity check
            if (conn->acl_recombination_pos == 0) {
                log_err( "ACL Cont Fragment but no first fragment for handle 0x%02x\n", con_handle);
                return;
            }

            // append fragment payload (header already stored)
            memcpy(&conn->acl_recombination_buffer[conn->acl_recombination_pos], &packet[4], acl_length );
            conn->acl_recombination_pos += acl_length;

            // log_err( "ACL Cont Fragment: acl_len %u, combined_len %u, l2cap_len %u\n",
            //        acl_length, connection->acl_recombination_pos, connection->acl_recombination_length);

            // forward complete L2CAP packet if complete.
            if (conn->acl_recombination_pos >= conn->acl_recombination_length + 4 + 4){ // pos already incl. ACL header

                hci_stack.packet_handler(HCI_ACL_DATA_PACKET, conn->acl_recombination_buffer, conn->acl_recombination_pos);
                // reset recombination buffer
                conn->acl_recombination_length = 0;
                conn->acl_recombination_pos = 0;
            }
            break;

        case 0x02: { // first fragment

            // sanity check
            if (conn->acl_recombination_pos) {
                log_err( "ACL First Fragment but data in buffer for handle 0x%02x\n", con_handle);
                return;
            }

            // peek into L2CAP packet!
            uint16_t l2cap_length = READ_L2CAP_LENGTH( packet );

            // compare fragment size to L2CAP packet size
            if (acl_length >= l2cap_length + 4){

                // forward fragment as L2CAP packet
                hci_stack.packet_handler(HCI_ACL_DATA_PACKET, packet, acl_length + 4);

            } else {
                // store first fragment and tweak acl length for complete package
                memcpy(conn->acl_recombination_buffer, packet, acl_length + 4);
                conn->acl_recombination_pos    = acl_length + 4;
                conn->acl_recombination_length = l2cap_length;
                bt_store_16(conn->acl_recombination_buffer, 2, acl_length +4);
                // log_err( "ACL First Fragment: acl_len %u, l2cap_len %u\n", acl_length, l2cap_length);
            }
            break;

        }
        default:
            log_err( "hci.c: acl_handler called with invalid packet boundary flags %u\n", acl_flags & 0x03);
            return;
    }

    // execute main loop
    hci_run();
}

static void hci_shutdown_connection(hci_connection_t *conn){
    log_dbg("Connection closed: handle %u, ", conn->con_handle);
    print_bd_addr( conn->address );
    log_dbg("\n");
    run_loop_remove_timer(&conn->timeout);
    linked_list_remove(&hci_stack.connections, (linked_item_t *) conn);
    free( conn );
    hci_emit_nr_connections_changed();
}

// avoid huge local variables
static device_name_t device_name;
static void event_handler(uint8_t *packet, int size){
    bd_addr_t addr;
    hci_con_handle_t handle;
    hci_connection_t * conn;
    int i;
    link_key_t link_key;

    // get num_cmd_packets
    if (packet[0] == HCI_EVENT_COMMAND_COMPLETE || packet[0] == HCI_EVENT_COMMAND_STATUS){
        // Get Num_HCI_Command_Packets
        hci_stack.num_cmd_packets = packet[2];
    }

    switch (packet[0]) {

        case HCI_EVENT_COMMAND_COMPLETE:
            if (COMMAND_COMPLETE_EVENT(packet, hci_read_buffer_size)){
                // from offset 5
                // status
                hci_stack.acl_data_packet_length = READ_BT_16(packet, 6);
                // ignore: SCO data packet len (8)
                hci_stack.total_num_acl_packets  = packet[9];
                // ignore: total num SCO packets
                if (hci_stack.state == HCI_STATE_INITIALIZING){
                    log_dbg("hci_read_buffer_size: size %u, count %u\n", hci_stack.acl_data_packet_length, hci_stack.total_num_acl_packets);
                }
            }
            if (COMMAND_COMPLETE_EVENT(packet, hci_write_scan_enable)){
                hci_emit_discoverable_enabled(hci_stack.discoverable);
            }
            break;

        case HCI_EVENT_NUMBER_OF_COMPLETED_PACKETS:
            for (i=0; i<packet[2];i++){
                handle = READ_BT_16(packet, 3 + 2*i);
                uint16_t num_packets = READ_BT_16(packet, 3 + packet[2]*2 + 2*i);
                conn = connection_for_handle(handle);
                if (!conn){
                    log_err("hci_number_completed_packet lists unused con handle %u\n", handle);
                    continue;
                }
                conn->num_acl_packets_sent -= num_packets;
                // log_dbg("hci_number_completed_packet %u processed for handle %u, outstanding %u\n", num_packets, handle, conn->num_acl_packets_sent);
            }
            break;

        case HCI_EVENT_CONNECTION_REQUEST:
            bt_flip_addr(addr, &packet[2]);
            // TODO: eval COD 8-10
            uint8_t link_type = packet[11];
            log_dbg("Connection_incoming: "); print_bd_addr(addr); log_dbg(", type %u\n", link_type);
            if (link_type == 1) { // ACL
                conn = connection_for_address(addr);
                if (!conn) {
                    conn = create_connection_for_addr(addr);
                }
                // TODO: check for malloc failure
                conn->state = ACCEPTED_CONNECTION_REQUEST;
                hci_send_cmd(&hci_accept_connection_request, addr, 1);
            } else {
                // TODO: decline request
            }
            break;

        case HCI_EVENT_CONNECTION_COMPLETE:
            // Connection management
            bt_flip_addr(addr, &packet[5]);
            log_dbg("Connection_complete (status=%u)", packet[2]); print_bd_addr(addr); log_dbg("\n");
            conn = connection_for_address(addr);
            if (conn) {
                if (!packet[2]){
                    conn->state = OPEN;
                    conn->con_handle = READ_BT_16(packet, 3);

                    gettimeofday(&conn->timestamp, NULL);
                    run_loop_set_timer(&conn->timeout, HCI_CONNECTION_TIMEOUT_MS);
                    run_loop_add_timer(&conn->timeout);

                    log_dbg("New connection: handle %u, ", conn->con_handle);
                    print_bd_addr( conn->address );
                    log_dbg("\n");

                    hci_emit_nr_connections_changed();
                } else {
                    // connection failed, remove entry
                    linked_list_remove(&hci_stack.connections, (linked_item_t *) conn);
                    free( conn );

                    // if authentication error, also delete link key
                    if (packet[2] == 0x05) {
                        hci_drop_link_key_for_bd_addr(&addr);
                    }
                }
            }
            break;

        case HCI_EVENT_LINK_KEY_REQUEST:
            hci_add_connection_flags_for_flipped_bd_addr(&packet[2], RECV_LINK_KEY_REQUEST);
            if (!hci_stack.remote_device_db) break;
            bt_flip_addr(addr, &packet[2]);
            if ( hci_stack.remote_device_db->get_link_key( &addr, &link_key)){
                hci_send_cmd(&hci_link_key_request_reply, &addr, &link_key);
            } else {
                hci_send_cmd(&hci_link_key_request_negative_reply, &addr);
            }
            // request already answered
            return;

        case HCI_EVENT_LINK_KEY_NOTIFICATION:
            hci_add_connection_flags_for_flipped_bd_addr(&packet[2], RECV_LINK_KEY_NOTIFICATION);
            if (!hci_stack.remote_device_db) break;
            bt_flip_addr(addr, &packet[2]);
            hci_stack.remote_device_db->put_link_key(&addr, (link_key_t *) &packet[8]);
            // still forward event to allow dismiss of pairing dialog
            break;

        case HCI_EVENT_PIN_CODE_REQUEST:
            hci_add_connection_flags_for_flipped_bd_addr(&packet[2], RECV_PIN_CODE_REQUEST);
            break;

        case HCI_EVENT_REMOTE_NAME_REQUEST_COMPLETE:
            if (!hci_stack.remote_device_db) break;
            if (packet[2]) break; // status not ok
            bt_flip_addr(addr, &packet[3]);
            bzero(&device_name, sizeof(device_name_t));
            strncpy((char*) device_name, (char*) &packet[9], 248);
            hci_stack.remote_device_db->put_name(&addr, &device_name);
            break;

        case HCI_EVENT_INQUIRY_RESULT:
        case HCI_EVENT_INQUIRY_RESULT_WITH_RSSI:
            if (!hci_stack.remote_device_db) break;
            // first send inq result packet
            hci_stack.packet_handler(HCI_EVENT_PACKET, packet, size);
            // then send cached remote names
            for (i=0; i<packet[2];i++){
                bt_flip_addr(addr, &packet[3+i*6]);
                if (hci_stack.remote_device_db->get_name(&addr, &device_name)){
                    hci_emit_remote_name_cached(&addr, &device_name);
                }
            }
            return;

        case HCI_EVENT_DISCONNECTION_COMPLETE:
            if (!packet[2]){
                handle = READ_BT_16(packet, 3);
                hci_connection_t * conn = connection_for_handle(handle);
                if (conn) {
                    hci_shutdown_connection(conn);
                }
            }
            break;

        default:
            break;
    }

    // handle BT initialization
    if (hci_stack.state == HCI_STATE_INITIALIZING){
        // handle H4 synchronization loss on restart
        // if (hci_stack.substate == 1 && packet[0] == HCI_EVENT_HARDWARE_ERROR){
        //    hci_stack.substate = 0;
        // }
        // handle normal init sequence
        if (hci_stack.substate % 2){
            // odd: waiting for event
            if (packet[0] == HCI_EVENT_COMMAND_COMPLETE){
                hci_stack.substate++;
            }
        }
    }

    // help with BT sleep
    if (hci_stack.state == HCI_STATE_FALLING_ASLEEP
        && hci_stack.substate == 1
        && COMMAND_COMPLETE_EVENT(packet, hci_write_scan_enable)){
        hci_stack.substate++;
    }

    hci_stack.packet_handler(HCI_EVENT_PACKET, packet, size);

	// execute main loop
	hci_run();
}

void packet_handler(uint8_t packet_type, uint8_t *packet, uint16_t size){
    switch (packet_type) {
        case HCI_EVENT_PACKET:
            event_handler(packet, size);
            break;
        case HCI_ACL_DATA_PACKET:
            acl_handler(packet, size);
            break;
        default:
            break;
    }
}

/** Register HCI packet handlers */
void hci_register_packet_handler(void (*handler)(uint8_t packet_type, uint8_t *packet, uint16_t size)){
    hci_stack.packet_handler = handler;
}

void hci_init(hci_transport_t *transport, void *config, bt_control_t *control, remote_device_db_t * remote_device_db){

    // reference to use transport layer implementation
    hci_stack.hci_transport = transport;

    // references to used control implementation
    hci_stack.control = control;

    // reference to used config
    hci_stack.config = config;

    // no connections yet
    hci_stack.connections = NULL;

    // empty cmd buffer
    hci_stack.hci_cmd_buffer = malloc(3+255);

    // higher level handler
    hci_stack.packet_handler = dummy_handler;

    // store and open remote device db
    hci_stack.remote_device_db = remote_device_db;
    if (hci_stack.remote_device_db) {
        hci_stack.remote_device_db->open();
    }

    // register packet handlers with transport
    transport->register_packet_handler(&packet_handler);
}

void hci_close(){
    // close remote device db
    if (hci_stack.remote_device_db) {
        hci_stack.remote_device_db->close();
    }
}

// State-Module-Driver overview
// state                    module  low-level
// HCI_STATE_OFF             off      close
// HCI_STATE_INITIALIZING,   on       open
// HCI_STATE_WORKING,        on       open
// HCI_STATE_HALTING,        on       open
// HCI_STATE_SLEEPING,    off/sleep   close
// HCI_STATE_FALLING_ASLEEP  on       open

static int hci_power_control_on(){

    // power on
    int err = 0;
    if (hci_stack.control && hci_stack.control->on){
        err = (*hci_stack.control->on)(hci_stack.config);
    }
    if (err){
        log_err( "POWER_ON failed\n");
        hci_emit_hci_open_failed();
        return err;
    }

    // open low-level device
    err = hci_stack.hci_transport->open(hci_stack.config);
    if (err){
        log_err( "HCI_INIT failed, turning Bluetooth off again\n");
        if (hci_stack.control && hci_stack.control->off){
            (*hci_stack.control->off)(hci_stack.config);
        }
        hci_emit_hci_open_failed();
        return err;
    }
    return 0;
}

static void hci_power_control_off(){

    // close low-level device
    hci_stack.hci_transport->close(hci_stack.config);

    // power off
    if (hci_stack.control && hci_stack.control->off){
        (*hci_stack.control->off)(hci_stack.config);
    }
    hci_stack.state = HCI_STATE_OFF;
}

static void hci_power_control_sleep(){

    log_dbg("hci_power_control_sleep");

#if 0
    // don't close serial port during sleep

    // close low-level device
    hci_stack.hci_transport->close(hci_stack.config);
#endif

    // sleep mode
    if (hci_stack.control && hci_stack.control->sleep){
        (*hci_stack.control->sleep)(hci_stack.config);
    }

    hci_stack.state = HCI_STATE_SLEEPING;
}

static int hci_power_control_wake(){

    log_dbg("hci_power_control_wake");

    // wake on
    if (hci_stack.control && hci_stack.control->wake){
        (*hci_stack.control->wake)(hci_stack.config);
    }

#if 0
    // open low-level device
    int err = hci_stack.hci_transport->open(hci_stack.config);
    if (err){
        log_err( "HCI_INIT failed, turning Bluetooth off again\n");
        if (hci_stack.control && hci_stack.control->off){
            (*hci_stack.control->off)(hci_stack.config);
        }
        hci_emit_hci_open_failed();
        return err;
    }
#endif

    return 0;
}


int hci_power_control(HCI_POWER_MODE power_mode){

    log_dbg("hci_power_control: %u\n", power_mode);

    int err = 0;
    switch (hci_stack.state){

        case HCI_STATE_OFF:
            switch (power_mode){
                case HCI_POWER_ON:
                    err = hci_power_control_on();
                    if (err) return err;
                    // set up state machine
                    hci_stack.num_cmd_packets = 1; // assume that one cmd can be sent
                    hci_stack.state = HCI_STATE_INITIALIZING;
                    hci_stack.substate = 0;
                    break;
                case HCI_POWER_OFF:
                    // do nothing
                    break;
                case HCI_POWER_SLEEP:
                    // do nothing (with SLEEP == OFF)
                    break;
            }
            break;

        case HCI_STATE_INITIALIZING:
            switch (power_mode){
                case HCI_POWER_ON:
                    // do nothing
                    break;
                case HCI_POWER_OFF:
                    // no connections yet, just turn it off
                    hci_power_control_off();
                    break;
                case HCI_POWER_SLEEP:
                    // no connections yet, just turn it off
                    hci_power_control_sleep();
                    break;
            }
            break;

        case HCI_STATE_WORKING:
            switch (power_mode){
                case HCI_POWER_ON:
                    // do nothing
                    break;
                case HCI_POWER_OFF:
                    // see hci_run
                    hci_stack.state = HCI_STATE_HALTING;
                    break;
                case HCI_POWER_SLEEP:
                    // see hci_run
                    hci_stack.state = HCI_STATE_FALLING_ASLEEP;
                    hci_stack.substate = 0;
                    break;
            }
            break;

        case HCI_STATE_HALTING:
            switch (power_mode){
                case HCI_POWER_ON:
                    // set up state machine
                    hci_stack.state = HCI_STATE_INITIALIZING;
                    hci_stack.substate = 0;
                    break;
                case HCI_POWER_OFF:
                    // do nothing
                    break;
                case HCI_POWER_SLEEP:
                    // see hci_run
                    hci_stack.state = HCI_STATE_FALLING_ASLEEP;
                    hci_stack.substate = 0;
                    break;
            }
            break;

        case HCI_STATE_FALLING_ASLEEP:
            switch (power_mode){
                case HCI_POWER_ON:
                    // set up state machine
                    hci_stack.num_cmd_packets = 1; // assume that one cmd can be sent
                    hci_stack.state = HCI_STATE_INITIALIZING;
                    hci_stack.substate = 0;
                    break;
                case HCI_POWER_OFF:
                    // see hci_run
                    hci_stack.state = HCI_STATE_HALTING;
                    break;
                case HCI_POWER_SLEEP:
                    // do nothing
                    break;
            }
            break;

        case HCI_STATE_SLEEPING:
            switch (power_mode){
                case HCI_POWER_ON:
                    err = hci_power_control_wake();
                    if (err) return err;
                    // set up state machine
                    hci_stack.num_cmd_packets = 1; // assume that one cmd can be sent
                    hci_stack.state = HCI_STATE_INITIALIZING;
                    hci_stack.substate = 0;
                    break;
                case HCI_POWER_OFF:
                    hci_stack.state = HCI_STATE_OFF;
                    break;
                case HCI_POWER_SLEEP:
                    // do nothing
                    break;
            }
            break;
    }

    // create internal event
	hci_emit_state();

	// trigger next/first action
	hci_run();

    return 0;
}

void hci_discoverable_control(uint8_t enable){
    if (enable) enable = 1; // normalize argument

    if (hci_stack.discoverable == enable){
        hci_emit_discoverable_enabled(hci_stack.discoverable);
        return;
    }

    hci_send_cmd(&hci_write_scan_enable, 2 | enable); // 1 = inq scan, 2 = page scan
    hci_stack.discoverable = enable;
}

void hci_run(){

    if (hci_stack.num_cmd_packets == 0) {
        // cannot send command yet
        return;
    }

    hci_connection_t * connection;

    switch (hci_stack.state){
        case HCI_STATE_INITIALIZING:
            if (hci_stack.substate % 2) {
                // odd: waiting for command completion
                return;
            }
            switch (hci_stack.substate >> 1){
                case 0:
                    hci_send_cmd(&hci_reset);
                    break;
                case 1:
                    // custom initialization
                    if (hci_stack.control && hci_stack.control->next_command){
                        uint8_t * cmd = (*hci_stack.control->next_command)(hci_stack.config);
                        if (cmd) {
                            int size = 3 + cmd[2];
                            hci_stack.hci_transport->send_packet(HCI_COMMAND_DATA_PACKET, cmd, size);
                            hci_stack.substate = 0; // more init commands
                            break;
                        }
                    }
                    // otherwise continue
					hci_send_cmd(&hci_read_bd_addr);
					break;
				case 2:
					hci_send_cmd(&hci_read_buffer_size);
					break;
                case 3:
                    // ca. 15 sec
                    hci_send_cmd(&hci_write_page_timeout, 0x6000);
                    break;
				case 4:
					hci_send_cmd(&hci_write_scan_enable, 2); // page scan
					break;
                case 5:
#ifndef EMBEDDED
                {
                    char hostname[30];
                    gethostname(hostname, 30);
                    hostname[29] = '\0';
                    hci_send_cmd(&hci_write_local_name, hostname);
                    break;
                }
                case 6:
#endif
                    // done.
                    hci_stack.state = HCI_STATE_WORKING;
                    hci_emit_state();
                    break;
                default:
                    break;
            }
            hci_stack.substate++;
            break;

        case HCI_STATE_HALTING:

            log_dbg("HCI_STATE_HALTING\n");
            // close all open connections
            connection =  (hci_connection_t *) hci_stack.connections;
            if (connection){
                log_dbg("HCI_STATE_HALTING, connection %u, handle %u\n", (int) connection, connection->con_handle);
                // send disconnect
                hci_send_cmd(&hci_disconnect, connection->con_handle, 0x13);  // remote closed connection

                // send disconnected event right away - causes higher layer connections to get closed, too.
                hci_shutdown_connection(connection);

                // remove from table
                hci_stack.connections = connection->item.next;
                return;
            }
            log_dbg("HCI_STATE_HALTING, calling off\n");

            // switch mode
            hci_power_control_off();
            hci_emit_state();
            log_dbg("HCI_STATE_HALTING, done\n");
            break;

        case HCI_STATE_FALLING_ASLEEP:
            switch(hci_stack.substate) {
                case 0:
                    log_dbg("HCI_STATE_FALLING_ASLEEP\n");
                    // close all open connections
                    connection =  (hci_connection_t *) hci_stack.connections;
                    if (connection){
                        log_dbg("HCI_STATE_FALLING_ASLEEP, connection %u, handle %u\n", (int) connection, connection->con_handle);
                        // send disconnect
                        hci_send_cmd(&hci_disconnect, connection->con_handle, 0x13);  // remote closed connection

                        // send disconnected event right away - causes higher layer connections to get closed, too.
                        hci_shutdown_connection(connection);

                        // remove from table
                        hci_stack.connections = connection->item.next;
                        return;
                    }

                    log_dbg("HCI_STATE_HALTING, disabling inq & page scans\n");

                    // disable page and inquiry scan
                    hci_send_cmd(&hci_write_scan_enable, 0); // none

                    // continue in next sub state
                    hci_stack.substate++;
                    break;
                case 1:
                    // wait for command complete "hci_write_scan_enable" in event_handler();
                    break;
                case 2:
                    log_dbg("HCI_STATE_HALTING, calling sleep\n");
                    // switch mode
                    hci_power_control_sleep();  // changes hci_stack.state to SLEEP
                    hci_emit_state();
                default:
                    break;
            }
            break;

        default:
            break;
    }
}

int hci_send_cmd_packet(uint8_t *packet, int size){
    bd_addr_t addr;
    hci_connection_t * conn;
    // house-keeping

    // create_connection?
    if (IS_COMMAND(packet, hci_create_connection)){
        bt_flip_addr(addr, &packet[3]);
        log_dbg("Create_connection to "); print_bd_addr(addr); log_dbg("\n");
        conn = connection_for_address(addr);
        if (conn) {
            // if connection exists
            if (conn->state == OPEN) {
                // if OPEN, emit connection complete command
                hci_emit_connection_complete(conn);
            }
            //    otherwise, just ignore
            return 0; // don't sent packet to controller

        } else{
            conn = create_connection_for_addr(addr);
            if (conn){
                //    create connection struct and register, state = SENT_CREATE_CONNECTION
                conn->state = SENT_CREATE_CONNECTION;
            }
        }
    }

    if (IS_COMMAND(packet, hci_link_key_request_reply)){
        hci_add_connection_flags_for_flipped_bd_addr(&packet[3], SENT_LINK_KEY_REPLY);
    }
    if (IS_COMMAND(packet, hci_link_key_request_negative_reply)){
        hci_add_connection_flags_for_flipped_bd_addr(&packet[3], SENT_LINK_KEY_NEGATIVE_REQUEST);
    }
    if (IS_COMMAND(packet, hci_pin_code_request_reply)){
        hci_add_connection_flags_for_flipped_bd_addr(&packet[3], SENT_PIN_CODE_REPLY);
    }
    if (IS_COMMAND(packet, hci_pin_code_request_negative_reply)){
        hci_add_connection_flags_for_flipped_bd_addr(&packet[3], SENT_PIN_CODE_NEGATIVE_REPLY);
    }

    if (IS_COMMAND(packet, hci_delete_stored_link_key)){
        if (hci_stack.remote_device_db){
            bt_flip_addr(addr, &packet[3]);
            hci_stack.remote_device_db->delete_link_key(&addr);
        }
    }

    hci_stack.num_cmd_packets--;
    return hci_stack.hci_transport->send_packet(HCI_COMMAND_DATA_PACKET, packet, size);
}

/**
 * pre: numcmds >= 0 - it's allowed to send a command to the controller
 */
int hci_send_cmd(const hci_cmd_t *cmd, ...){
    va_list argptr;
    va_start(argptr, cmd);
    uint8_t * hci_cmd_buffer = hci_stack.hci_cmd_buffer;
    uint16_t size = hci_create_cmd_internal(hci_stack.hci_cmd_buffer, cmd, argptr);
    va_end(argptr);
    return hci_send_cmd_packet(hci_cmd_buffer, size);
}

// Create various non-HCI events.
// TODO: generalize, use table similar to hci_create_command

void hci_emit_state(){
    uint8_t len = 3;
    uint8_t event[len];
    event[0] = BTSTACK_EVENT_STATE;
    event[1] = len - 3;
    event[2] = hci_stack.state;
    hci_dump_packet( HCI_EVENT_PACKET, 0, event, len);
    hci_stack.packet_handler(HCI_EVENT_PACKET, event, len);
}

void hci_emit_connection_complete(hci_connection_t *conn){
    uint8_t len = 13;
    uint8_t event[len];
    event[0] = HCI_EVENT_CONNECTION_COMPLETE;
    event[1] = len - 3;
    event[2] = 0; // status = OK
    bt_store_16(event, 3, conn->con_handle);
    bt_flip_addr(&event[5], conn->address);
    event[11] = 1; // ACL connection
    event[12] = 0; // encryption disabled
    hci_dump_packet( HCI_EVENT_PACKET, 0, event, len);
    hci_stack.packet_handler(HCI_EVENT_PACKET, event, len);
}

void hci_emit_l2cap_check_timeout(hci_connection_t *conn){
    uint8_t len = 4;
    uint8_t event[len];
    event[0] = L2CAP_EVENT_TIMEOUT_CHECK;
    event[1] = len - 2;
    bt_store_16(event, 2, conn->con_handle);
    hci_dump_packet( HCI_EVENT_PACKET, 0, event, len);
    hci_stack.packet_handler(HCI_EVENT_PACKET, event, len);
}

void hci_emit_nr_connections_changed(){
    uint8_t len = 3;
    uint8_t event[len];
    event[0] = BTSTACK_EVENT_NR_CONNECTIONS_CHANGED;
    event[1] = len - 2;
    event[2] = nr_hci_connections();
    hci_dump_packet( HCI_EVENT_PACKET, 0, event, len);
    hci_stack.packet_handler(HCI_EVENT_PACKET, event, len);
}

void hci_emit_hci_open_failed(){
    uint8_t len = 2;
    uint8_t event[len];
    event[0] = BTSTACK_EVENT_POWERON_FAILED;
    event[1] = len - 2;
    hci_dump_packet( HCI_EVENT_PACKET, 0, event, len);
    hci_stack.packet_handler(HCI_EVENT_PACKET, event, len);
}


void hci_emit_btstack_version() {
    uint8_t len = 6;
    uint8_t event[len];
    event[0] = BTSTACK_EVENT_VERSION;
    event[1] = len - 2;
    event[len++] = BTSTACK_MAJOR;
    event[len++] = BTSTACK_MINOR;
    bt_store_16(event, len, BTSTACK_REVISION);
    hci_dump_packet( HCI_EVENT_PACKET, 0, event, len);
    hci_stack.packet_handler(HCI_EVENT_PACKET, event, len);
}

void hci_emit_system_bluetooth_enabled(uint8_t enabled){
    uint8_t len = 3;
    uint8_t event[len];
    event[0] = BTSTACK_EVENT_SYSTEM_BLUETOOTH_ENABLED;
    event[1] = len - 2;
    event[2] = enabled;
    hci_dump_packet( HCI_EVENT_PACKET, 0, event, len);
    hci_stack.packet_handler(HCI_EVENT_PACKET, event, len);
}

void hci_emit_remote_name_cached(bd_addr_t *addr, device_name_t *name){
    uint16_t len = 2+1+6+248;
    uint8_t event[len];
    event[0] = BTSTACK_EVENT_REMOTE_NAME_CACHED;
    event[1] = len - 2;
    event[2] = 0;   // just to be compatible with HCI_EVENT_REMOTE_NAME_REQUEST_COMPLETE
    bt_flip_addr(&event[3], *addr);
    memcpy(&event[9], name, 248);
    hci_dump_packet(HCI_EVENT_PACKET, 0, event, len);
    hci_stack.packet_handler(HCI_EVENT_PACKET, event, len);
}

void hci_emit_discoverable_enabled(uint8_t enabled){
    uint8_t len = 3;
    uint8_t event[len];
    event[0] = BTSTACK_EVENT_DISCOVERABLE_ENABLED;
    event[1] = len - 2;
    event[2] = enabled;
    hci_dump_packet( HCI_EVENT_PACKET, 0, event, len);
    hci_stack.packet_handler(HCI_EVENT_PACKET, event, len);
}