rem: avrok = 0;
add: avr_cmd(fd, cmd, res);
context: int avr_program_enable ( int fd ){  unsigned char data[4] = {0xac, 0x53, 0x00, 0x00};  unsigned char byte, rbyte;  int avrok;  int i;  avrok = 0;  for (i=0; i<4; i++) {    byte = data[i];    rbyte = avr_txrx ( fd, byte );    if (i == 2) {      if (rbyte == data[1])        avrok = 1;    }  }  if (!avrok)    return -1;  return 0;}