_comedi_buf_read_free
nbytes = _comedi_buf_read_free(s, nbytes);
_comedi_buf_read_free(s, nbytes);
bi.bytes_read = _comedi_buf_read_free(s, bi.bytes_read);
_comedi_buf_read_free(s, n);
unsigned int _comedi_buf_read_free(struct comedi_subdevice *s,