if (ioctl (fd, SG_IO, &sg_io))
{
	return -1;
}

fd = open (file, O_RDWR|O_NONBLOCK)

/* synchronous SCSI command ioctl, (only in version 3 interface) */
#define SG_IO 0x2285   /* similar effect as write() followed by read() */

typedef struct sg_io_hdr
{
  int interface_id;           /* [i] 'S' for SCSI generic (required) */
  int dxfer_direction;        /* [i] data transfer direction  */
  unsigned char cmd_len;      /* [i] SCSI command length ( <= 16 bytes) */
  unsigned char mx_sb_len;    /* [i] max length to write to sbp */
  unsigned short int iovec_count; /* [i] 0 implies no scatter gather */
  unsigned int dxfer_len;     /* [i] byte count of data transfer */
  void * dxferp;              /* [i], [*io] points to data transfer memory
				 or scatter gather list */
  unsigned char * cmdp;       /* [i], [*i] points to command to perform */
  unsigned char * sbp;        /* [i], [*o] points to sense_buffer memory */
  unsigned int timeout;       /* [i] MAX_UINT->no timeout (unit: millisec) */
  unsigned int flags;         /* [i] 0 -> default, see SG_FLAG... */
  int pack_id;                /* [i->o] unused internally (normally) */
  void * usr_ptr;             /* [i->o] unused internally */
  unsigned char status;       /* [o] scsi status */
  unsigned char masked_status;/* [o] shifted, masked scsi status */
  unsigned char msg_status;   /* [o] messaging level data (optional) */
  unsigned char sb_len_wr;    /* [o] byte count actually written to sbp */
  unsigned short int host_status; /* [o] errors from host adapter */
  unsigned short int driver_status;/* [o] errors from software driver */
  int resid;                  /* [o] dxfer_len - actual_transferred */
  unsigned int duration;      /* [o] time taken by cmd (unit: millisec) */
  unsigned int info;          /* [o] auxiliary information */
} sg_io_hdr_t;

int err = 0;
Scsi_Command cmd;
cmd.associate (device);

cmd[0] = 0x35; // Synchronize Cache
cmd[1] = 0x00; // Immed
cmd[2] = 0x00; // Logical Block Address (drive may ignore this)
cmd[3] = 0x00; // Logical Block Address (drive may ignore this)
cmd[4] = 0x00; // Logical Block Address (drive may ignore this)
cmd[5] = 0x00; // Logical Block Address (drive may ignore this)

cmd[6] = 0x00; // Reserved
cmd[7] = 0x00; // Number of blocks (drive may ignore this)
cmd[8] = 0x00; // Number of blocks (drive may ignore this)
cmd[9] = 0x00; // Control

err = cmd.transport (); // -> ioctl
// err = cmd.transport (WRITE, buffer, 4); // testing

return err;

SendScsiCommand(hbd, output, prds, SCSI_PASS_THROUGH_DIRECT_ENGINE.SCSI_IOCTL_DATA_OUT, counter, mem);

 int interface_id;           // set to 'S'
  int dxfer_direction;        // -1, -2, -3 (none, write, read) all tested
  unsigned char cmd_len;      // is 12
  unsigned char mx_sb_len;    // is 64 (sg_io.mx_sb_len = sizeof(_sense))
  unsigned short int iovec_count; // is 0
  unsigned int dxfer_len;     // the length of my data buffer
  void * dxferp;              // my data buffer (unsigned char *) i have tested many possibilities (NULL, 1, 2, 3, 4 .... ;) )
  unsigned char * cmdp;       // my command buffer (MMC command, struct cdrom_generic_command)
  unsigned char * sbp;        // Sense buffer (sg_io.sbp = _sense.u)

union
{
	struct request_sense s; // request_sense is defined in cdrom.h
	unsigned char u[18];
} _sense;


  unsigned int timeout;       // MAX_UINT-> no timeout
  unsigned int flags;         // sg_io.flags = SG_FLAG_LUN_INHIBIT | SG_FLAG_DIRECT_IO;
  int pack_id;                /* [i->o] unused internally (normally) */
  void * usr_ptr;             /* [i->o] unused internally */
  unsigned char status;       // is 0
  unsigned char masked_status;// is 0
  unsigned char msg_status;   // is 0
  unsigned char sb_len_wr;    // is 0
  unsigned short int host_status; // is 0
  unsigned short int driver_status;// is 0
  int resid;                  // is 0
  unsigned int duration;      // is 0
  unsigned int info;          // is 0