Bluetooth: hci_h4: add serdev support - #526
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The H4 protocol has no serdev driver, so a controller that speaks plain H4 over a UART can only be attached with hciattach from userspace. Boards that describe it in the device tree get nothing. Add a serdev driver alongside the existing tty line discipline. It registers its own hci_uart_proto rather than reusing h4p, because giving h4p a ->setup would suppress the tty path's vendor detection. The AIC8800 ignores commands until it has answered one, so its match data asks for a quirk that sends HCI Reset until the controller replies; without it every early command times out and setup fails. Signed-off-by: Artem Butusov <art.sormy@gmail.com>
WalkthroughAdds a Devicetree binding for the AICsemi AIC8800 Bluetooth H4 serial controller. Extends Estimated code review effort: 3 (Moderate) | ~25 minutes Merge Risk: 🟡 Moderate · up to The PR adds serdev support for H4 Bluetooth devices, but its registration path can leave the serdev driver registered when a later registration step fails, creating partial initialization and cleanup risk. This should be fixed or explicitly accepted before merge. 🚥 Pre-merge checks | ✅ 5✅ Passed checks (5 passed)
✨ Finishing Touches🧪 Generate unit tests (beta)
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Inline comments:
In `@drivers/bluetooth/hci_h4.c`:
- Around line 241-262: Update h4_serdev_register and h4_init to propagate the
serdev_device_driver_register result; if hci_uart_register_proto(&h4p) fails,
call h4_serdev_unregister before returning the protocol-registration error,
while preserving the no-serdev configuration behavior.
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📒 Files selected for processing (2)
Documentation/devicetree/bindings/net/aicsemi-bluetooth.yamldrivers/bluetooth/hci_h4.c
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H4 has no serdev driver, so a controller speaking plain H4 over a UART can only be
attached with
hciattach; a board that describes it in the device tree gets nothing.Adds a serdev driver alongside the existing line discipline. It registers its own
hci_uart_protorather than reusingh4p, because givingh4pa->setupwouldsuppress the tty path's vendor detection.
The AIC8800 ignores commands until it has answered one, so its match data asks for a
quirk that retries HCI Reset; without it every early command times out.
Follows the conventions in
hci_ll/hci_bcm: serdev driver registered inh4_init()before the proto, flow control set once the port is open (
hci_serdev.copens itbefore calling
->open).Verified on an RK3528 box with an AIC8800 on uart2 — the driver binds against
aicsemi,aic8800-bt(/sys/bus/serial/devices/serial0-0/driver→hci_uart_h4),hci0registers asBus: UARTand reachesUP RUNNINGwitherrors:0, andbtmgmt findreturns devices. The quirk is visible doing its job: the first HCIReset times out and a retry succeeds.
Unrelated to this driver:
hci0starts rfkill-soft-blocked on a fresh image, becauserfkill-bthardcodes that; it needs onerfkill unblock bluetooth, whichsystemd-rfkill then persists.