_comedi_buf_write_alloc
nbytes = _comedi_buf_write_alloc(s, nbytes);
nbytes = _comedi_buf_write_alloc(s, nbytes);
_comedi_buf_write_alloc(s, bi.bytes_written);
_comedi_buf_write_alloc(s, async->prealloc_bufsz);
unsigned int _comedi_buf_write_alloc(struct comedi_subdevice *s,