ibrd
read_ret = ibrd(board, board->buffer, (board->buffer_length < remain) ?
int ibrd(struct gpib_board *board, u8 *buf, size_t length, int *end_flag, size_t *bytes_read);
unsigned int lcr_h, ibrd, fbrd;
ibrd = pl011_read(uap, REG_IBRD);
*baud = uap->port.uartclk * 4 / (64 * ibrd + fbrd);