Fix Bluetooth on T2 Macs by loading hci_bcm4377 module

[fedesapuppo]

Summary

• Bluetooth doesn't work on T2 Macs because the hci_bcm4377 kernel module isn't auto-loaded
• The apple-bcm-firmware package is already installed but the driver module was missing from /etc/modules-load.d/t2.conf
• Adds hci_bcm4377 to the T2 install script for new installs
• Adds a migration to append the module for existing T2 installs (with detection + idempotency guard)

Fixes #4402

Test plan

• Tested on MacBook Pro T2 — Bluetooth devices connect successfully after reboot
• Migration is a no-op on non-T2 hardware (PCI ID check gates it)
• Migration is idempotent (grep guard prevents duplicate entries)

[Copilot]

Pull request overview

This PR fixes Bluetooth on Apple T2 Macs by ensuring the hci_bcm4377 kernel module is loaded automatically at boot, both for new installs and for existing systems via a migration.

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Changes:

• Append hci_bcm4377 to /etc/modules-load.d/t2.conf during T2 hardware setup for new installs.
• Add a migration that detects T2 hardware and appends hci_bcm4377 to /etc/modules-load.d/t2.conf with an idempotency guard.

Reviewed changes

Copilot reviewed 2 out of 2 changed files in this pull request and generated 1 comment.

File	Description
migrations/1774642699.sh	Adds a T2-gated migration to persist module auto-loading for existing installs.
install/config/hardware/apple/fix-t2.sh	Ensures new T2 installs include hci_bcm4377 in the modules-load configuration.

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[Copilot]

The idempotency guard uses grep -q "hci_bcm4377" which will also match commented/disabled lines (e.g., # hci_bcm4377) or other text containing the substring, causing the migration to skip adding the actual module line. Consider making the check match an actual modules-load entry (e.g., exact line match after trimming whitespace, and ignoring comments) so the migration reliably fixes broken setups while still remaining idempotent.

Suggested change

	if ! grep -q "hci_bcm4377" /etc/modules-load.d/t2.conf 2>/dev/null; then
	if ! grep -qE '^[[:space:]]*hci_bcm4377[[:space:]]*$' /etc/modules-load.d/t2.conf 2>/dev/null; then