#define ARRAY_SIZE(a) \
         (sizeof(a) / sizeof((a)[0]))
 static int transfer(int fd_spi)
 {
     int ret, i;
     __u8 transmit_data[]={0x00,0x00,0x00};
     __u8 receive_data[] ={0x00,0x00,0x00};
     struct spi_ioc_transfer transfer_struct;

     transfer_struct.tx_buf =
         (unsigned long)transmit_data;
     transfer_struct.rx_buf =
         (unsigned long)receive_data;
     transfer_struct.len =
         ARRAY_SIZE(transmit_data);
     transfer_struct.delay_usecs = 0;
     transfer_struct.speed_hz = 10000;
     transfer_struct.bits_per_word = 8;

     ret = ioctl(fd_spi, SPI_IOC_MESSAGE(1),
         &transfer_struct);
     if (ret < 1) {
         fprintf(stderr,"xfer failed\n");
         return -1;
     }
     printf("Received: ");
     for (i=0;i<ARRAY_SIZE(receive_data);
         i++)
         printf("0x%x ", receive_data[i]);
     printf("\n");
     return 0;
 }