mixer_ioctl_cmd
ret = mixer_ioctl_cmd(d->mixer_dev, xcmd, arg, -1, td,
ret = mixer_ioctl_cmd(d->mixer_dev, cmd, arg, -1, td,
ret = mixer_ioctl_cmd(d->mixer_dev, cmd, arg, -1, td,
ret = mixer_ioctl_cmd(i_dev, cmd, arg, mode, td,
int mixer_ioctl_cmd(struct cdev *i_dev, u_long cmd, caddr_t arg, int mode, struct thread *td, int from);