aic8800d80/tests/issue63-btusb-zlp/README.md

Issue #63: system btusb ZLP test

This test keeps the normal aic_load_fw + btusb architecture. It does not restore or install the vendor aic_btusb driver.

The patch adds one quirk to the standard Linux btusb source:

• match only AICSemi 368b:8d81;
• set URB_ZERO_PACKET on Bluetooth ACL bulk OUT transfers;
• leave every other btusb device and code path unchanged.

The test installer downloads the standard btusb source matching the running kernel's upstream version, applies the patch, and installs the resulting btusb.ko through DKMS. The distribution module is not overwritten and can be restored by removing the DKMS test package.

Install the test module

On Fedora, make sure the test build dependencies are installed:

sudo dnf install dkms gcc make kernel-devel-$(uname -r) curl patch

Stop Bluetooth scanning and disconnect Bluetooth devices, then run:

cd tests/issue63-btusb-zlp
sudo ./btusb-zlp-test.sh install
./btusb-zlp-test.sh status

modinfo -n btusb should point to an updates/dkms path. Secure Boot systems may require the DKMS module to be signed or enrolled before it can load.

Select AAC again and play audio for at least one hour:

bluetoothctl scan off
pactl set-card-profile bluez_card.28_6F_40_46_AB_B1 a2dp-sink-aac

Please capture sudo btmon -w issue63-zlp.btsnoop and relevant dmesg lines if the connection still stalls.

Restore the distribution module

sudo ./btusb-zlp-test.sh remove
./btusb-zlp-test.sh status

After removal, modinfo -n btusb should point back to the distribution's kernel/drivers/bluetooth/btusb.ko path.

Scope

This is an A/B diagnostic patch, not a production workaround. If AAC remains stable, the small kernel patch can be submitted upstream. If it still fails, the next isolated experiment should add an AIC-specific runtime-PM quirk rather than replacing the standard Bluetooth driver.