int
acpi_register_ioctl(u_long cmd, acpi_ioctl_fn fn, void *arg)
{
    struct acpi_ioctl_hook      *hp;

        printf("acpi_register_ioctl: allocating acpi_ioctl_hook\n");
    if ((hp = malloc(sizeof(*hp), M_ACPIDEV, M_NOWAIT)) == NULL)
        return (ENOMEM);
    hp->cmd = cmd;
    hp->fn = fn;
    hp->arg = arg;

        printf("acpi_register_ioctl: ACPI_LOCK(acpi)\n");
    ACPI_LOCK(acpi);
    if (acpi_ioctl_hooks_initted == 0) {
        printf("acpi_register_ioctl: TAILQ_INIT\n");
        TAILQ_INIT(&acpi_ioctl_hooks);
        acpi_ioctl_hooks_initted = 1;
    }
        printf("acpi_register_ioctl: TAILQ_INSERT_TAIL\n");
    TAILQ_INSERT_TAIL(&acpi_ioctl_hooks, hp, link);
        printf("acpi_register_ioctl: ACPI_UNLOCK(acpi)\n");
    ACPI_UNLOCK(acpi);
        printf("acpi_register_ioctl: finished\n");

    return (0);
}