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Bluetooth Initialization

D-Bus Auto-Activation Sequence

Analysis of Nickel's Bluetooth initialization (strace output, 7678 lines) revealed the exact D-Bus sequence used.

Timeline

15:18:19.863567 - Nickel calls BluedroidManager1.On()
                  Service doesn't exist, D-Bus queues the call

15:18:19.947362 - D-Bus auto-starts service (84ms later)
                  NameOwnerChanged: com.kobo.mtk.bluedroid → :1.2

15:18:22.986149 - Bluetooth adapter ready (3.1 seconds after start)
                  InterfacesAdded: /org/bluez/hci0 with org.bluez.Adapter1

Key Finding: A single D-Bus method call (BluedroidManager1.On()) triggers the entire initialization sequence via D-Bus auto-activation.

Initialization Commands

Full Initialization Script

#!/usr/bin/env bash
# Enable Bluetooth on Kobo

echo "Step 1: Call On() method - triggers D-Bus auto-activation (this command blocks until initialization is complete)"
dbus-send --system --print-reply \
    --dest=com.kobo.mtk.bluedroid \
    / \
    com.kobo.bluetooth.BluedroidManager1.On

# No need to wait after On(); the command only returns when initialization is done

echo "Step 2: Power on the adapter"
dbus-send --system --print-reply \
    --dest=com.kobo.mtk.bluedroid \
    /org/bluez/hci0 \
    org.freedesktop.DBus.Properties.Set \
    string:org.bluez.Adapter1 \
    string:Powered \
    variant:boolean:true

echo "Step 3: Verify adapter is powered"
dbus-send --system --print-reply \
    --dest=com.kobo.mtk.bluedroid \
    /org/bluez/hci0 \
    org.freedesktop.DBus.Properties.Get \
    string:org.bluez.Adapter1 \
    string:Powered

Critical Notes

  1. Use com.kobo.mtk.bluedroid as destination for all D-Bus calls, not org.bluez
  2. Auto-activation - D-Bus starts the service automatically when the method is called
  3. The object paths still use /org/bluez/hci0 but the service name is com.kobo.mtk.bluedroid

Verification

# Check if processes started
ps aux | grep -E "(mtkbtd|btservice)" | grep -v grep

# Check if service is registered
dbus-send --system --print-reply \
    --dest=org.freedesktop.DBus \
    /org/freedesktop/DBus \
    org.freedesktop.DBus.ListNames | grep "com.kobo.mtk.bluedroid"

# Check adapter properties
dbus-send --system --print-reply \
    --dest=com.kobo.mtk.bluedroid \
    /org/bluez/hci0 \
    org.freedesktop.DBus.Properties.GetAll \
    string:org.bluez.Adapter1