modules/bluetooth/backend-ofono.c

/***
  This file is part of PulseAudio.

  Copyright 2013 João Paulo Rechi Vita

  PulseAudio is free software; you can redistribute it and/or modify
  it under the terms of the GNU Lesser General Public License as
  published by the Free Software Foundation; either version 2.1 of the
  License, or (at your option) any later version.

  PulseAudio is distributed in the hope that it will be useful, but
  WITHOUT ANY WARRANTY; without even the implied warranty of
  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
  General Public License for more details.

  You should have received a copy of the GNU Lesser General Public
  License along with PulseAudio; if not, see <http://www.gnu.org/licenses/>.
***/

#ifdef HAVE_CONFIG_H
#include <config.h>
#endif

#include <errno.h>
#include <poll.h>

#include <pulsecore/core-util.h>
#include <pulsecore/dbus-shared.h>
#include <pulsecore/shared.h>
#include <pulsecore/core-error.h>

#include "bluez5-util.h"

#define HFP_AUDIO_CODEC_CVSD    0x01
#define HFP_AUDIO_CODEC_MSBC    0x02

#define OFONO_SERVICE "org.ofono"
#define HF_AUDIO_AGENT_INTERFACE OFONO_SERVICE ".HandsfreeAudioAgent"
#define HF_AUDIO_MANAGER_INTERFACE OFONO_SERVICE ".HandsfreeAudioManager"

#define HF_AUDIO_AGENT_PATH "/HandsfreeAudioAgent"

#define HF_AUDIO_AGENT_XML                                          \
    DBUS_INTROSPECT_1_0_XML_DOCTYPE_DECL_NODE                       \
    "<node>"                                                        \
    "  <interface name=\"org.freedesktop.DBus.Introspectable\">"    \
    "    <method name=\"Introspect\">"                              \
    "      <arg direction=\"out\" type=\"s\" />"                    \
    "    </method>"                                                 \
    "  </interface>"                                                \
    "  <interface name=\"org.ofono.HandsfreeAudioAgent\">"          \
    "    <method name=\"Release\">"                                 \
    "    </method>"                                                 \
    "    <method name=\"NewConnection\">"                           \
    "      <arg direction=\"in\"  type=\"o\" name=\"card_path\" />" \
    "      <arg direction=\"in\"  type=\"h\" name=\"sco_fd\" />"    \
    "      <arg direction=\"in\"  type=\"y\" name=\"codec\" />"     \
    "    </method>"                                                 \
    "  </interface>"                                                \
    "</node>"

struct hf_audio_card {
    pa_bluetooth_backend *backend;
    char *path;
    char *remote_address;
    char *local_address;

    bool connecting;
    int fd;
    int (*acquire)(struct hf_audio_card *card);

    pa_bluetooth_transport *transport;
    pa_hook_slot *device_unlink_slot;
};

struct pa_bluetooth_backend {
    pa_core *core;
    pa_bluetooth_discovery *discovery;
    pa_dbus_connection *connection;
    pa_hashmap *cards;
    char *ofono_bus_id;

    PA_LLIST_HEAD(pa_dbus_pending, pending);
};

static pa_dbus_pending* hf_dbus_send_and_add_to_pending(pa_bluetooth_backend *backend, DBusMessage *m,
                                                    DBusPendingCallNotifyFunction func, void *call_data) {
    pa_dbus_pending *p;
    DBusPendingCall *call;

    pa_assert(backend);
    pa_assert(m);

    pa_assert_se(dbus_connection_send_with_reply(pa_dbus_connection_get(backend->connection), m, &call, -1));

    p = pa_dbus_pending_new(pa_dbus_connection_get(backend->connection), m, call, backend, call_data);
    PA_LLIST_PREPEND(pa_dbus_pending, backend->pending, p);
    dbus_pending_call_set_notify(call, func, p, NULL);

    return p;
}

static DBusMessage *card_send(struct hf_audio_card *card, const char *method, DBusError *err)
{
    pa_bluetooth_transport *t = card->transport;
    DBusMessage *m, *r;

    pa_assert_se(m = dbus_message_new_method_call(t->owner, t->path, "org.ofono.HandsfreeAudioCard", method));
    r = dbus_connection_send_with_reply_and_block(pa_dbus_connection_get(card->backend->connection), m, -1, err);
    dbus_message_unref(m);

    return r;
}

static int card_connect(struct hf_audio_card *card) {
    DBusMessage *r;
    DBusError err;

    if (card->connecting)
        return -EAGAIN;

    card->connecting = true;

    dbus_error_init(&err);
    r = card_send(card, "Connect", &err);

    if (!r) {
        pa_log_error("Failed to connect %s: %s", err.name, err.message);
        card->connecting = false;
        dbus_error_free(&err);
        return -1;
    }

    dbus_message_unref(r);

    if (card->connecting)
        return -EAGAIN;

    return 0;
}

static int card_acquire(struct hf_audio_card *card) {
    int fd;
    uint8_t codec;
    DBusMessage *r;
    DBusError err;

    /* Try acquiring the stream first which was introduced in 1.21 */
    dbus_error_init(&err);
    r = card_send(card, "Acquire", &err);

    if (!r) {
        if (!pa_streq(err.name, DBUS_ERROR_UNKNOWN_METHOD)) {
            pa_log_error("Failed to acquire %s: %s", err.name, err.message);
            dbus_error_free(&err);
            return -1;
        }
        dbus_error_free(&err);
        /* Fallback to Connect as this might be an old version of ofono */
        card->acquire = card_connect;
        return card_connect(card);
    }

    if ((dbus_message_get_args(r, NULL, DBUS_TYPE_UNIX_FD, &fd,
                                      DBUS_TYPE_BYTE, &codec,
                                      DBUS_TYPE_INVALID) == true)) {
        dbus_message_unref(r);
        if (codec != HFP_AUDIO_CODEC_CVSD) {
            pa_log_error("Invalid codec: %u", codec);
            /* shutdown to make sure connection is dropped immediately */
            shutdown(fd, SHUT_RDWR);
            close(fd);
            return -1;
        }
        card->transport->codec = codec;
        card->fd = fd;
        return 0;
    }

    pa_log_error("Unable to acquire");
    dbus_message_unref(r);
    return -1;
}

static void hf_audio_agent_card_removed(pa_bluetooth_backend *backend, const char *path);

static pa_hook_result_t device_unlink_cb(pa_bluetooth_discovery *y, const pa_bluetooth_device *d, struct hf_audio_card *card) {
    pa_assert(d);
    pa_assert(card);

    hf_audio_agent_card_removed(card->backend, card->path);

    return PA_HOOK_OK;
}

static struct hf_audio_card *hf_audio_card_new(pa_bluetooth_backend *backend, const char *path) {
    struct hf_audio_card *card = pa_xnew0(struct hf_audio_card, 1);

    card->path = pa_xstrdup(path);
    card->backend = backend;
    card->fd = -1;
    card->acquire = card_acquire;

    card->device_unlink_slot = pa_hook_connect(pa_bluetooth_discovery_hook(backend->discovery, PA_BLUETOOTH_HOOK_DEVICE_UNLINK),
                                               PA_HOOK_NORMAL, (pa_hook_cb_t) device_unlink_cb, card);

    return card;
}

static void hf_audio_card_free(struct hf_audio_card *card) {
    pa_assert(card);

    if (card->device_unlink_slot)
        pa_hook_slot_free(card->device_unlink_slot);

    if (card->transport)
        pa_bluetooth_transport_free(card->transport);

    pa_xfree(card->path);
    pa_xfree(card->remote_address);
    pa_xfree(card->local_address);
    pa_xfree(card);
}

static int socket_accept(int sock)
{
    char c;
    struct pollfd pfd;

    if (sock < 0)
        return -ENOTCONN;

    memset(&pfd, 0, sizeof(pfd));
    pfd.fd = sock;
    pfd.events = POLLOUT;

    if (poll(&pfd, 1, 0) < 0)
        return -errno;

    /*
     * If socket already writable then it is not in defer setup state,
     * otherwise it needs to be read to authorize the connection.
     */
    if ((pfd.revents & POLLOUT))
        return 0;

    /* Enable socket by reading 1 byte */
    if (read(sock, &c, 1) < 0)
        return -errno;

    return 0;
}

static int hf_audio_agent_transport_acquire(pa_bluetooth_transport *t, bool optional, size_t *imtu, size_t *omtu) {
    struct hf_audio_card *card = t->userdata;
    int err;

    pa_assert(card);

    if (!optional && card->fd < 0) {
        err = card->acquire(card);
        if (err < 0)
            return err;
    }

    /* The correct block size should take into account the SCO MTU from
     * the Bluetooth adapter and (for adapters in the USB bus) the MxPS
     * value from the Isoc USB endpoint in use by btusb and should be
     * made available to userspace by the Bluetooth kernel subsystem.
     * Meanwhile the empiric value 48 will be used. */
    if (imtu)
        *imtu = 48;
    if (omtu)
        *omtu = 48;

    err = socket_accept(card->fd);
    if (err < 0) {
        pa_log_error("Deferred setup failed on fd %d: %s", card->fd, pa_cstrerror(-err));
        return -1;
    }

    return card->fd;
}

static void hf_audio_agent_transport_release(pa_bluetooth_transport *t) {
    struct hf_audio_card *card = t->userdata;

    pa_assert(card);

    if (card->fd < 0) {
        pa_log_info("Transport %s already released", t->path);
        return;
    }

    /* shutdown to make sure connection is dropped immediately */
    shutdown(card->fd, SHUT_RDWR);
    close(card->fd);
    card->fd = -1;
}

static void hf_audio_agent_card_found(pa_bluetooth_backend *backend, const char *path, DBusMessageIter *props_i) {
    DBusMessageIter i, value_i;
    const char *key, *value;
    struct hf_audio_card *card;
    pa_bluetooth_device *d;
    pa_bluetooth_profile_t p = PA_BLUETOOTH_PROFILE_HEADSET_AUDIO_GATEWAY;

    pa_assert(backend);
    pa_assert(path);
    pa_assert(props_i);

    pa_log_debug("New HF card found: %s", path);

    card = hf_audio_card_new(backend, path);

    while (dbus_message_iter_get_arg_type(props_i) != DBUS_TYPE_INVALID) {
        char c;

        dbus_message_iter_recurse(props_i, &i);

        dbus_message_iter_get_basic(&i, &key);
        dbus_message_iter_next(&i);
        dbus_message_iter_recurse(&i, &value_i);

        if ((c = dbus_message_iter_get_arg_type(&value_i)) != DBUS_TYPE_STRING) {
            pa_log_error("Invalid properties for %s: expected 's', received '%c'", path, c);
            goto fail;
        }

        dbus_message_iter_get_basic(&value_i, &value);

        if (pa_streq(key, "RemoteAddress")) {
            pa_xfree(card->remote_address);
            card->remote_address = pa_xstrdup(value);
        } else if (pa_streq(key, "LocalAddress")) {
            pa_xfree(card->local_address);
            card->local_address = pa_xstrdup(value);
        } else if (pa_streq(key, "Type")) {
            if (pa_streq(value, "gateway"))
                p = PA_BLUETOOTH_PROFILE_HEADSET_HEAD_UNIT;
        }

        pa_log_debug("%s: %s", key, value);

        dbus_message_iter_next(props_i);
    }

    d = pa_bluetooth_discovery_get_device_by_address(backend->discovery, card->remote_address, card->local_address);
    if (!d) {
        pa_log_error("Device doesnt exist for %s", path);
        goto fail;
    }

    card->transport = pa_bluetooth_transport_new(d, backend->ofono_bus_id, path, p, NULL, 0);
    card->transport->acquire = hf_audio_agent_transport_acquire;
    card->transport->release = hf_audio_agent_transport_release;
    card->transport->userdata = card;

    pa_bluetooth_transport_put(card->transport);
    pa_hashmap_put(backend->cards, card->path, card);

    return;

fail:
    hf_audio_card_free(card);
}

static void hf_audio_agent_card_removed(pa_bluetooth_backend *backend, const char *path) {
    struct hf_audio_card *card;

    pa_assert(backend);
    pa_assert(path);

    pa_log_debug("HF card removed: %s", path);

    card = pa_hashmap_remove(backend->cards, path);
    if (!card)
        return;

    hf_audio_card_free(card);
}

static void hf_audio_agent_get_cards_reply(DBusPendingCall *pending, void *userdata) {
    DBusMessage *r;
    pa_dbus_pending *p;
    pa_bluetooth_backend *backend;
    DBusMessageIter i, array_i, struct_i, props_i;

    pa_assert_se(p = userdata);
    pa_assert_se(backend = p->context_data);
    pa_assert_se(r = dbus_pending_call_steal_reply(pending));

    if (dbus_message_get_type(r) == DBUS_MESSAGE_TYPE_ERROR) {
        pa_log_error("Failed to get a list of handsfree audio cards from ofono: %s: %s",
                     dbus_message_get_error_name(r), pa_dbus_get_error_message(r));
        goto finish;
    }

    if (!dbus_message_iter_init(r, &i) || !pa_streq(dbus_message_get_signature(r), "a(oa{sv})")) {
        pa_log_error("Invalid arguments in GetCards() reply");
        goto finish;
    }

    dbus_message_iter_recurse(&i, &array_i);
    while (dbus_message_iter_get_arg_type(&array_i) != DBUS_TYPE_INVALID) {
        const char *path;

        dbus_message_iter_recurse(&array_i, &struct_i);
        dbus_message_iter_get_basic(&struct_i, &path);
        dbus_message_iter_next(&struct_i);

        dbus_message_iter_recurse(&struct_i, &props_i);

        hf_audio_agent_card_found(backend, path, &props_i);

        dbus_message_iter_next(&array_i);
    }

finish:
    dbus_message_unref(r);

    PA_LLIST_REMOVE(pa_dbus_pending, backend->pending, p);
    pa_dbus_pending_free(p);
}

static void hf_audio_agent_get_cards(pa_bluetooth_backend *hf) {
    DBusMessage *m;

    pa_assert(hf);

    pa_assert_se(m = dbus_message_new_method_call(OFONO_SERVICE, "/", HF_AUDIO_MANAGER_INTERFACE, "GetCards"));
    hf_dbus_send_and_add_to_pending(hf, m, hf_audio_agent_get_cards_reply, NULL);
}

static void ofono_bus_id_destroy(pa_bluetooth_backend *backend) {
    pa_hashmap_remove_all(backend->cards);

    if (backend->ofono_bus_id) {
        pa_xfree(backend->ofono_bus_id);
        backend->ofono_bus_id = NULL;
        pa_bluetooth_discovery_set_ofono_running(backend->discovery, false);
    }
}

static void hf_audio_agent_register_reply(DBusPendingCall *pending, void *userdata) {
    DBusMessage *r;
    pa_dbus_pending *p;
    pa_bluetooth_backend *backend;

    pa_assert_se(p = userdata);
    pa_assert_se(backend = p->context_data);
    pa_assert_se(r = dbus_pending_call_steal_reply(pending));

    if (dbus_message_get_type(r) == DBUS_MESSAGE_TYPE_ERROR) {
        pa_log_info("Failed to register as a handsfree audio agent with ofono: %s: %s",
                    dbus_message_get_error_name(r), pa_dbus_get_error_message(r));
        goto finish;
    }

    backend->ofono_bus_id = pa_xstrdup(dbus_message_get_sender(r));

    hf_audio_agent_get_cards(backend);

finish:
    dbus_message_unref(r);

    PA_LLIST_REMOVE(pa_dbus_pending, backend->pending, p);
    pa_dbus_pending_free(p);

    pa_bluetooth_discovery_set_ofono_running(backend->discovery, backend->ofono_bus_id != NULL);
}

static void hf_audio_agent_register(pa_bluetooth_backend *hf) {
    DBusMessage *m;
    uint8_t codecs[2];
    const uint8_t *pcodecs = codecs;
    int ncodecs = 0;
    const char *path = HF_AUDIO_AGENT_PATH;

    pa_assert(hf);

    pa_assert_se(m = dbus_message_new_method_call(OFONO_SERVICE, "/", HF_AUDIO_MANAGER_INTERFACE, "Register"));

    codecs[ncodecs++] = HFP_AUDIO_CODEC_CVSD;

    pa_assert_se(dbus_message_append_args(m, DBUS_TYPE_OBJECT_PATH, &path, DBUS_TYPE_ARRAY, DBUS_TYPE_BYTE, &pcodecs, ncodecs,
                                          DBUS_TYPE_INVALID));

    hf_dbus_send_and_add_to_pending(hf, m, hf_audio_agent_register_reply, NULL);
}

static void hf_audio_agent_unregister(pa_bluetooth_backend *backend) {
    DBusMessage *m;
    const char *path = HF_AUDIO_AGENT_PATH;

    pa_assert(backend);
    pa_assert(backend->connection);

    if (backend->ofono_bus_id) {
        pa_assert_se(m = dbus_message_new_method_call(backend->ofono_bus_id, "/", HF_AUDIO_MANAGER_INTERFACE, "Unregister"));
        pa_assert_se(dbus_message_append_args(m, DBUS_TYPE_OBJECT_PATH, &path, DBUS_TYPE_INVALID));
        pa_assert_se(dbus_connection_send(pa_dbus_connection_get(backend->connection), m, NULL));

        ofono_bus_id_destroy(backend);
    }
}

static DBusHandlerResult filter_cb(DBusConnection *bus, DBusMessage *m, void *data) {
    const char *sender;
    DBusError err;
    pa_bluetooth_backend *backend = data;

    pa_assert(bus);
    pa_assert(m);
    pa_assert(backend);

    sender = dbus_message_get_sender(m);
    if (!pa_safe_streq(backend->ofono_bus_id, sender) && !pa_streq("org.freedesktop.DBus", sender))
        return DBUS_HANDLER_RESULT_NOT_YET_HANDLED;

    dbus_error_init(&err);

    if (dbus_message_is_signal(m, "org.freedesktop.DBus", "NameOwnerChanged")) {
        const char *name, *old_owner, *new_owner;

        if (!dbus_message_get_args(m, &err,
                                   DBUS_TYPE_STRING, &name,
                                   DBUS_TYPE_STRING, &old_owner,
                                   DBUS_TYPE_STRING, &new_owner,
                                   DBUS_TYPE_INVALID)) {
            pa_log_error("Failed to parse org.freedesktop.DBus.NameOwnerChanged: %s", err.message);
            goto fail;
        }

        if (pa_streq(name, OFONO_SERVICE)) {

            if (old_owner && *old_owner) {
                pa_log_debug("oFono disappeared");
                ofono_bus_id_destroy(backend);
            }

            if (new_owner && *new_owner) {
                pa_log_debug("oFono appeared");
                hf_audio_agent_register(backend);
            }
        }

    } else if (dbus_message_is_signal(m, "org.ofono.HandsfreeAudioManager", "CardAdded")) {
        const char *p;
        DBusMessageIter arg_i, props_i;

        if (!dbus_message_iter_init(m, &arg_i) || !pa_streq(dbus_message_get_signature(m), "oa{sv}")) {
            pa_log_error("Failed to parse org.ofono.HandsfreeAudioManager.CardAdded");
            goto fail;
        }

        dbus_message_iter_get_basic(&arg_i, &p);

        pa_assert_se(dbus_message_iter_next(&arg_i));
        pa_assert(dbus_message_iter_get_arg_type(&arg_i) == DBUS_TYPE_ARRAY);

        dbus_message_iter_recurse(&arg_i, &props_i);

        hf_audio_agent_card_found(backend, p, &props_i);
    } else if (dbus_message_is_signal(m, "org.ofono.HandsfreeAudioManager", "CardRemoved")) {
        const char *p;

        if (!dbus_message_get_args(m, &err, DBUS_TYPE_OBJECT_PATH, &p, DBUS_TYPE_INVALID)) {
            pa_log_error("Failed to parse org.ofono.HandsfreeAudioManager.CardRemoved: %s", err.message);
            goto fail;
        }

        hf_audio_agent_card_removed(backend, p);
    }

fail:
    dbus_error_free(&err);
    return DBUS_HANDLER_RESULT_NOT_YET_HANDLED;
}

static DBusMessage *hf_audio_agent_release(DBusConnection *c, DBusMessage *m, void *data) {
    DBusMessage *r;
    const char *sender;
    pa_bluetooth_backend *backend = data;

    pa_assert(backend);

    sender = dbus_message_get_sender(m);
    if (!pa_safe_streq(backend->ofono_bus_id, sender)) {
        pa_assert_se(r = dbus_message_new_error(m, "org.ofono.Error.NotAllowed", "Operation is not allowed by this sender"));
        return r;
    }

    pa_log_debug("HF audio agent has been unregistered by oFono (%s)", backend->ofono_bus_id);

    ofono_bus_id_destroy(backend);

    pa_assert_se(r = dbus_message_new_method_return(m));

    return r;
}

static DBusMessage *hf_audio_agent_new_connection(DBusConnection *c, DBusMessage *m, void *data) {
    DBusMessage *r;
    const char *sender, *path;
    int fd;
    uint8_t codec;
    struct hf_audio_card *card;
    pa_bluetooth_backend *backend = data;

    pa_assert(backend);

    sender = dbus_message_get_sender(m);
    if (!pa_safe_streq(backend->ofono_bus_id, sender)) {
        pa_assert_se(r = dbus_message_new_error(m, "org.ofono.Error.NotAllowed", "Operation is not allowed by this sender"));
        return r;
    }

    if (dbus_message_get_args(m, NULL,
                              DBUS_TYPE_OBJECT_PATH, &path,
                              DBUS_TYPE_UNIX_FD, &fd,
                              DBUS_TYPE_BYTE, &codec,
                              DBUS_TYPE_INVALID) == FALSE) {
        pa_assert_se(r = dbus_message_new_error(m, "org.ofono.Error.InvalidArguments", "Invalid arguments in method call"));
        return r;
    }

    card = pa_hashmap_get(backend->cards, path);

    if (!card || codec != HFP_AUDIO_CODEC_CVSD || card->fd >= 0) {
        pa_log_warn("New audio connection invalid arguments (path=%s fd=%d, codec=%d)", path, fd, codec);
        pa_assert_se(r = dbus_message_new_error(m, "org.ofono.Error.InvalidArguments", "Invalid arguments in method call"));
        shutdown(fd, SHUT_RDWR);
        close(fd);
        return r;
    }

    pa_log_debug("New audio connection on card %s (fd=%d, codec=%d)", path, fd, codec);

    card->connecting = false;
    card->fd = fd;
    card->transport->codec = codec;

    pa_bluetooth_transport_set_state(card->transport, PA_BLUETOOTH_TRANSPORT_STATE_PLAYING);

    pa_assert_se(r = dbus_message_new_method_return(m));

    return r;
}

static DBusHandlerResult hf_audio_agent_handler(DBusConnection *c, DBusMessage *m, void *data) {
    pa_bluetooth_backend *backend = data;
    DBusMessage *r = NULL;
    const char *path, *interface, *member;

    pa_assert(backend);

    path = dbus_message_get_path(m);
    interface = dbus_message_get_interface(m);
    member = dbus_message_get_member(m);

    if (!pa_streq(path, HF_AUDIO_AGENT_PATH))
        return DBUS_HANDLER_RESULT_NOT_YET_HANDLED;

    pa_log_debug("dbus: path=%s, interface=%s, member=%s", path, interface, member);

    if (dbus_message_is_method_call(m, "org.freedesktop.DBus.Introspectable", "Introspect")) {
        const char *xml = HF_AUDIO_AGENT_XML;

        pa_assert_se(r = dbus_message_new_method_return(m));
        pa_assert_se(dbus_message_append_args(r, DBUS_TYPE_STRING, &xml, DBUS_TYPE_INVALID));

    } else if (dbus_message_is_method_call(m, HF_AUDIO_AGENT_INTERFACE, "NewConnection"))
        r = hf_audio_agent_new_connection(c, m, data);
    else if (dbus_message_is_method_call(m, HF_AUDIO_AGENT_INTERFACE, "Release"))
        r = hf_audio_agent_release(c, m, data);
    else
        return DBUS_HANDLER_RESULT_NOT_YET_HANDLED;

    if (r) {
        pa_assert_se(dbus_connection_send(pa_dbus_connection_get(backend->connection), r, NULL));
        dbus_message_unref(r);
    }

    return DBUS_HANDLER_RESULT_HANDLED;
}

pa_bluetooth_backend *pa_bluetooth_ofono_backend_new(pa_core *c, pa_bluetooth_discovery *y) {
    pa_bluetooth_backend *backend;
    DBusError err;
    static const DBusObjectPathVTable vtable_hf_audio_agent = {
        .message_function = hf_audio_agent_handler,
    };

    pa_assert(c);

    backend = pa_xnew0(pa_bluetooth_backend, 1);
    backend->core = c;
    backend->discovery = y;
    backend->cards = pa_hashmap_new_full(pa_idxset_string_hash_func, pa_idxset_string_compare_func, NULL,
                                         (pa_free_cb_t) hf_audio_card_free);

    dbus_error_init(&err);

    if (!(backend->connection = pa_dbus_bus_get(c, DBUS_BUS_SYSTEM, &err))) {
        pa_log("Failed to get D-Bus connection: %s", err.message);
        dbus_error_free(&err);
        pa_xfree(backend);
        return NULL;
    }

    /* dynamic detection of handsfree audio cards */
    if (!dbus_connection_add_filter(pa_dbus_connection_get(backend->connection), filter_cb, backend, NULL)) {
        pa_log_error("Failed to add filter function");
        pa_dbus_connection_unref(backend->connection);
        pa_xfree(backend);
        return NULL;
    }

    if (pa_dbus_add_matches(pa_dbus_connection_get(backend->connection), &err,
            "type='signal',sender='org.freedesktop.DBus',interface='org.freedesktop.DBus',member='NameOwnerChanged',"
            "arg0='" OFONO_SERVICE "'",
            "type='signal',sender='" OFONO_SERVICE "',interface='" HF_AUDIO_MANAGER_INTERFACE "',member='CardAdded'",
            "type='signal',sender='" OFONO_SERVICE "',interface='" HF_AUDIO_MANAGER_INTERFACE "',member='CardRemoved'",
            NULL) < 0) {
        pa_log("Failed to add oFono D-Bus matches: %s", err.message);
        dbus_connection_remove_filter(pa_dbus_connection_get(backend->connection), filter_cb, backend);
        pa_dbus_connection_unref(backend->connection);
        pa_xfree(backend);
        return NULL;
    }

    pa_assert_se(dbus_connection_register_object_path(pa_dbus_connection_get(backend->connection), HF_AUDIO_AGENT_PATH,
                                                      &vtable_hf_audio_agent, backend));

    hf_audio_agent_register(backend);

    return backend;
}

void pa_bluetooth_ofono_backend_free(pa_bluetooth_backend *backend) {
    pa_assert(backend);

    pa_dbus_free_pending_list(&backend->pending);

    hf_audio_agent_unregister(backend);

    dbus_connection_unregister_object_path(pa_dbus_connection_get(backend->connection), HF_AUDIO_AGENT_PATH);

    pa_dbus_remove_matches(pa_dbus_connection_get(backend->connection),
            "type='signal',sender='org.freedesktop.DBus',interface='org.freedesktop.DBus',member='NameOwnerChanged',"
            "arg0='" OFONO_SERVICE "'",
            "type='signal',sender='" OFONO_SERVICE "',interface='" HF_AUDIO_MANAGER_INTERFACE "',member='CardAdded'",
            "type='signal',sender='" OFONO_SERVICE "',interface='" HF_AUDIO_MANAGER_INTERFACE "',member='CardRemoved'",
            NULL);

    dbus_connection_remove_filter(pa_dbus_connection_get(backend->connection), filter_cb, backend);

    pa_dbus_connection_unref(backend->connection);

    pa_hashmap_free(backend->cards);

    pa_xfree(backend);
}