Week 15

Progress summary for Week 15 (August 31-September 6, 2026) of the AGL Bluetooth Integration project.

This week, the Bluetooth pairing feature merged into flutter-ics-homescreen, and I documented the PipeWire native-HFP call path over D-Bus.

Status#

  • Status: Completed
  • Timeline: August 31, 2026 to September 6, 2026
  • Merged change: AGL Gerrit 31887

Progress#

1. Bluetooth Pairing Merged into flutter-ics-homescreen#

Gerrit change 31887, which adds the pairing UI and bluez_native support, has merged. The homescreen now has the reviewed Bluetooth pairing and device-management foundation needed by the media and telephony work.

The Yocto layer also requires AGL's flutter-app-plugins.bbclass updates to compile the bluez_native library: the initial addition in Gerrit 31977 and its follow-up fixes in Gerrit 31989.

2. Studied PipeWire Bluetooth Phone Calls over D-Bus#

The study established the following implementation and validation points:

  • Configure WirePlumber's native HFP backend with bluez5.telephony.use-system-bus = true; AGL's split system services do not have a user session bus.

    # 30-AGL-bluetooth.conf
monitor.bluez.properties = {
  bluez5.hfphsp-backend = "native"
  bluez5.telephony.use-system-bus = true
}

  • Retain oFono for SIM and modem support, but remove its bluez PACKAGECONFIG so PipeWire is the sole Bluetooth HFP owner.

    # ofono_%.bbappend
PACKAGECONFIG:remove = "bluez"

  • Discover the dynamic Audio Gateway (agN) and call (callN) objects through org.freedesktop.DBus.ObjectManager.GetManagedObjects; object suffixes must not be hard-coded.

    busctl --system call \
  org.pipewire.Telephony /org/pipewire/Telephony \
  org.freedesktop.DBus.ObjectManager GetManagedObjects

    Raspberry Pi 5 validation confirmed that the system-bus name is owned by the Bluetooth WirePlumber instance and exposed the connected phone as ag1:

    root@raspberrypi5:~# busctl --system status org.pipewire.Telephony
PID=457
PIDFD=yes
PPID=1
TTY=n/a
UID=1008
EUID=1008
SUID=1008
FSUID=1008
GID=1008
EGID=1008
SGID=1008
FSGID=1008
SupplementaryGIDs=29 44 1008
Comm=wireplumber
Exe=/usr/bin/wireplumber
CommandLine=/usr/bin/wireplumber -p bluetooth
CGroup=/system.slice/system-wireplumber.slice/wireplumber@bluetooth.service
Unit=wireplumber@bluetooth.service
Slice=system-wireplumber.slice
UserUnit=n/a
UserSlice=n/a
Session=n/a
AuditLoginUID=n/a
AuditSessionID=n/a
UniqueName=:1.12
EffectiveCapabilities=cap_sys_nice
PermittedCapabilities=cap_sys_nice
InheritableCapabilities=cap_setpcap cap_sys_admin cap_sys_nice
BoundingCapabilities=cap_chown cap_dac_override cap_dac_read_search
       cap_fowner cap_fsetid cap_kill cap_setgid
       cap_setuid cap_setpcap cap_linux_immutable cap_net_bind_service
       cap_net_broadcast cap_net_admin cap_net_raw cap_ipc_lock
       cap_ipc_owner cap_sys_module cap_sys_rawio cap_sys_chroot
       cap_sys_ptrace cap_sys_pacct cap_sys_admin cap_sys_boot
       cap_sys_nice cap_sys_resource cap_sys_time cap_sys_tty_config
       cap_mknod cap_lease cap_audit_write cap_audit_control
       cap_setfcap cap_mac_override cap_mac_admin cap_syslog
       cap_wake_alarm cap_block_suspend cap_audit_read cap_perfmon
       cap_bpf cap_checkpoint_restore

root@raspberrypi5:~# busctl --system call org.pipewire.Telephony /org/pipewire/Telephony \
  org.freedesktop.DBus.ObjectManager GetManagedObjects
a{oa{sa{sv}}} 1 "/org/pipewire/Telephony/ag1" 2 "org.pipewire.Telephony.AudioGateway1" 3 "Address" s "04:C8:B0:EC:DE:0F" "SpeakerVolume" y 15 "MicrophoneVolume" y 15 "org.pipewire.Telephony.AudioGatewayTransport1" 3 "Codec" y 0 "State" s "idle" "RejectSCO" b false
root@raspberrypi5:~#

  • Monitor InterfacesAdded, InterfacesRemoved, and PropertiesChanged to keep the UI synchronized with call state.

    busctl --system monitor org.pipewire.Telephony

  • Verify both D-Bus state and the PipeWire graph: an active call must activate the SCO transport and provide the HFP downlink to vehicle speakers and uplink from the vehicle microphone.

    busctl --system get-property \
  org.pipewire.Telephony "$AG" \
  org.pipewire.Telephony.AudioGatewayTransport1 State
PIPEWIRE_RUNTIME_DIR=/run/pipewire wpctl status
PIPEWIRE_RUNTIME_DIR=/run/pipewire pw-link -l

  • Grant the agl-driver application user narrow system-D-Bus permission to send messages to org.pipewire.Telephony; a broad default-user rule would allow arbitrary local users to control calls.

    <!-- wireplumber-bluetooth.conf -->
<policy user="agl-driver">
  <allow send_destination="org.pipewire.Telephony"/>
</policy>

The detailed command workflow is captured in the Hands-Free Profile guide, including gateway and call discovery, outgoing and incoming calls, call state inspection, and SCO transport checks.

Next Steps#

  • Start the homescreen integration for PipeWire telephony call state and controls.
  • Validate the native Flutter plugin build path with the merged homescreen Bluetooth feature.
  • Exercise D-Bus call control and SCO audio routing on the Raspberry Pi 5.