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Bluetooth Module Parameters for Apple Devices

This document describes the kernel module parameters used to optimize Bluetooth functionality on Apple devices.

Overview

The file config/modprobe.d/bluetooth-apple.conf contains carefully tuned parameters for Apple Bluetooth hardware. These parameters address various issues discovered during our technical investigation documented in docs/technical/technical-findings.md.

Parameter Details

bluetooth Module

options bluetooth disable_ertm=1 disable_esco=0
  • disable_ertm=1 - Disable Enhanced Re-Transmission Mode, which can cause connection issues with Apple devices due to timing constraints
  • disable_esco=0 - Enable Enhanced SCO for better audio quality with Apple audio devices

btusb Module

options btusb reset=1 external_amp=0 esco=1
  • reset=1 - Forces a hardware reset during module initialization, addressing the BCM reset failures common on Apple hardware
  • external_amp=0 - Disables external amplifier support which is not used in Apple devices and can cause conflicts
  • esco=1 - Enables enhanced SCO (eSCO) support for better audio quality in Bluetooth audio devices

apple_bce Module (if present)

options apple_bce power_save=0
  • power_save=0 - Disables power saving features in the Apple BCE (Broadcom) driver which can cause stability issues and connection drops

USB Core Configuration

options usbcore autosuspend=-1
  • autosuspend=-1 - Completely disables USB autosuspend for Bluetooth devices, preventing power management from causing device resets

Module Dependencies

softdep btusb pre: btintel btbcm bluetooth
  • Ensures the kernel modules load in the correct sequence for Apple hardware
  • The sequence is essential: bluetooth → btbcm → btintel → btusb → apple_bce

Installation

To install these parameters system-wide:

sudo mkdir -p /etc/modprobe.d/
sudo cp config/modprobe.d/bluetooth-apple.conf /etc/modprobe.d/
sudo update-initramfs -u    # On Debian/Ubuntu systems
sudo dracut -f               # On Fedora/RHEL systems

Testing

After installation, reboot the system and verify that parameters are applied:

systool -vm btusb | grep -A2 parameters

Parameters should match those specified in the configuration file.