This looks good. My only worry is that there is a theoretical maximum of 65535 interrupts that can be specified in _AEI (currently we limit it to 255, but with _EVT support it grows to 65535), and having even 255 gpiobus children seems ... not good. Maybe we could make it so one instance of gpioaei can handle multiple pins, or even merge the driver into acpi_gpiobus and handle it there.