[pulseaudio-discuss] [RFC v1 11/14] bluetooth: Update to new BlueZ 5 transport acquire/release API

[Mikel Astiz]

From: Mikel Astiz <mikel.astiz at bmw-carit.de>

The new D-Bus API doesn't support access rights, which weren't used by
PulseAudio anyway, but it does solve a race condition: now optional
acquires can be implemented by bluetooth-util atomically using the D-Bus
TryAcquire() method.
---
 src/modules/bluetooth/bluetooth-util.c          | 66 +++++++++++++++----------
 src/modules/bluetooth/module-bluetooth-device.c |  8 +--
 2 files changed, 42 insertions(+), 32 deletions(-)

diff --git a/src/modules/bluetooth/bluetooth-util.c b/src/modules/bluetooth/bluetooth-util.c
index bd5b315..cd6e74a 100644
--- a/src/modules/bluetooth/bluetooth-util.c
+++ b/src/modules/bluetooth/bluetooth-util.c
@@ -1426,40 +1426,52 @@ bool pa_bluetooth_device_any_audio_connected(const pa_bluetooth_device *d) {
 }
 
 int pa_bluetooth_transport_acquire(pa_bluetooth_transport *t, bool optional, size_t *imtu, size_t *omtu) {
-    const char *accesstype = "rw";
-    const char *interface;
     DBusMessage *m, *r;
     DBusError err;
     int ret;
     uint16_t i, o;
+    const char *method;
 
     pa_assert(t);
     pa_assert(t->device);
     pa_assert(t->device->discovery);
 
-    interface = t->device->discovery->version == BLUEZ_VERSION_4 ? "org.bluez.MediaTransport" : "org.bluez.MediaTransport1";
-
-    if (optional) {
-        /* FIXME: we are trying to acquire the transport only if the stream is
-           playing, without actually initiating the stream request from our side
-           (which is typically undesireable specially for hfgw use-cases.
-           However this approach is racy, since the stream could have been
-           suspended in the meantime, so we can't really guarantee that the
-           stream will not be requested until BlueZ's API supports this
-           atomically. */
-        if (t->state < PA_BLUETOOTH_TRANSPORT_STATE_PLAYING) {
-            pa_log_info("Failed optional acquire of transport %s", t->path);
-            return -1;
+    dbus_error_init(&err);
+
+    if (t->device->discovery->version == BLUEZ_VERSION_4) {
+        const char *accesstype = "rw";
+
+        if (optional) {
+            /* We are trying to acquire the transport only if the stream is
+               playing, without actually initiating the stream request from our side
+               (which is typically undesireable specially for hfgw use-cases.
+               However this approach is racy, since the stream could have been
+               suspended in the meantime, so we can't really guarantee that the
+               stream will not be requested with the API in BlueZ 4.x */
+            if (t->state < PA_BLUETOOTH_TRANSPORT_STATE_PLAYING) {
+                pa_log_info("Failed optional acquire of unavailable transport %s", t->path);
+                return -1;
+            }
         }
-    }
 
-    dbus_error_init(&err);
+        method = "Acquire";
+        pa_assert_se(m = dbus_message_new_method_call(t->owner, t->path, "org.bluez.MediaTransport", method));
+        pa_assert_se(dbus_message_append_args(m, DBUS_TYPE_STRING, &accesstype, DBUS_TYPE_INVALID));
+    } else {
+        pa_assert(t->device->discovery->version == BLUEZ_VERSION_5);
+
+        method = optional ? "TryAcquire" : "Acquire";
+        pa_assert_se(m = dbus_message_new_method_call(t->owner, t->path, "org.bluez.MediaTransport1", method));
+    }
 
-    pa_assert_se(m = dbus_message_new_method_call(t->owner, t->path, interface, "Acquire"));
-    pa_assert_se(dbus_message_append_args(m, DBUS_TYPE_STRING, &accesstype, DBUS_TYPE_INVALID));
     r = dbus_connection_send_with_reply_and_block(pa_dbus_connection_get(t->device->discovery->connection), m, -1, &err);
 
     if (!r) {
+        if (optional && pa_streq(err.name, "org.bluez.Error.NotAvailable"))
+            pa_log_info("Failed optional acquire of unavailable transport %s", t->path);
+        else
+            pa_log("Transport %s() failed for transport %s (%s)", method, t->path, err.message);
+
         dbus_error_free(&err);
         return -1;
     }
@@ -1484,8 +1496,6 @@ fail:
 }
 
 void pa_bluetooth_transport_release(pa_bluetooth_transport *t) {
-    const char *accesstype = "rw";
-    const char *interface;
     DBusMessage *m;
     DBusError err;
 
@@ -1493,12 +1503,18 @@ void pa_bluetooth_transport_release(pa_bluetooth_transport *t) {
     pa_assert(t->device);
     pa_assert(t->device->discovery);
 
-    interface = t->device->discovery->version == BLUEZ_VERSION_4 ? "org.bluez.MediaTransport" : "org.bluez.MediaTransport1";
-
     dbus_error_init(&err);
 
-    pa_assert_se(m = dbus_message_new_method_call(t->owner, t->path, interface, "Release"));
-    pa_assert_se(dbus_message_append_args(m, DBUS_TYPE_STRING, &accesstype, DBUS_TYPE_INVALID));
+    if (t->device->discovery->version == BLUEZ_VERSION_4) {
+        const char *accesstype = "rw";
+
+        pa_assert_se(m = dbus_message_new_method_call(t->owner, t->path, "org.bluez.MediaTransport", "Release"));
+        pa_assert_se(dbus_message_append_args(m, DBUS_TYPE_STRING, &accesstype, DBUS_TYPE_INVALID));
+    } else {
+        pa_assert(t->device->discovery->version == BLUEZ_VERSION_5);
+        pa_assert_se(m = dbus_message_new_method_call(t->owner, t->path, "org.bluez.MediaTransport1", "Release"));
+    }
+
     dbus_connection_send_with_reply_and_block(pa_dbus_connection_get(t->device->discovery->connection), m, -1, &err);
 
     if (dbus_error_is_set(&err)) {
diff --git a/src/modules/bluetooth/module-bluetooth-device.c b/src/modules/bluetooth/module-bluetooth-device.c
index becf716..8d52318 100644
--- a/src/modules/bluetooth/module-bluetooth-device.c
+++ b/src/modules/bluetooth/module-bluetooth-device.c
@@ -360,14 +360,8 @@ static int bt_transport_acquire(struct userdata *u, bool optional) {
     pa_log_debug("Acquiring transport %s", u->transport->path);
 
     u->stream_fd = pa_bluetooth_transport_acquire(u->transport, optional, &u->read_link_mtu, &u->write_link_mtu);
-    if (u->stream_fd < 0) {
-        if (!optional)
-            pa_log("Failed to acquire transport %s", u->transport->path);
-        else
-            pa_log_info("Failed optional acquire of transport %s", u->transport->path);
-
+    if (u->stream_fd < 0)
         return -1;
-    }
 
     u->transport_acquired = true;
     pa_log_info("Transport %s acquired: fd %d", u->transport->path, u->stream_fd);
-- 
1.7.11.7