LinuxQuestions.org - Setting the read speed of a dvd drive

As everyone knows, the speed of the cdrom drive can be set using hdparm. However, this is not working for dvd drives reading dvd discs.
I found a solution, after a lot of useless searching, and since I didn't see any reference of the problem here (or a complete description of it anywhere), for easy reach, in case anyone else needs it/
This might not be the right board, so I ask the mods to move it, if necessary.
The thing goes like this:
First compile the code below (thanks go to Thomas Fritzsche for it)

Code:

/*

 * SpeedControl - use SET STREAMING command to set the speed of DVD-drives

 *      

 *

 * Copyright (c) 2004        Thomas Fritzsche <tf@noto.de>

 *

 *  This program is free software; you can redistribute it and/or modify

 *  it under the terms of the GNU General Public License as published by

 *  the Free Software Foundation; either version 2 of the License, or

 *  (at your option) any later version.

 *

 *  This program is distributed in the hope that it will be useful,

 *  but WITHOUT ANY WARRANTY; without even the implied warranty of

 *  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the

 *  GNU General Public License for more details.

 *

 *  You should have received a copy of the GNU General Public License

 *  along with this program; if not, write to the Free Software

 *  Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.

 *

 */



#include <stdio.h>

#include <stdlib.h>

#include <fcntl.h>

#include <string.h>

#include <unistd.h>

#include <sys/ioctl.h>

#include <linux/cdrom.h>



 

void dump_sense(unsigned char *cdb, struct request_sense *sense)

{

  int i;

  

  printf("Command failed: ");

    

  for (i=0; i<12; i++)

    printf("%02x ", cdb[i]);

          

    if (sense) {

      printf(" - sense: %02x.%02x.%02x\n", sense->sense_key, sense->asc,

              sense->ascq);

    } else {

      printf(", no sense\n");

    }

}



int main(int argc, char *argv[])

{

  char *device = "/dev/cdrom";

  int c,fd;

  int speed = 0;

  unsigned long rw_size;

  

  unsigned char buffer[28];

  

  struct cdrom_generic_command cgc;

  struct request_sense sense;

  extern char * optarg;



  while((c=getopt(argc,argv,"x:"))!=EOF) {

    switch(c) {

      case 'x': speed = atoi(optarg); break;

      default:

        printf("Usage: speedcontrol [-x speed] [device]");

        return -1;

    }

  }



  if (argc > optind) device = argv[optind];

  

  fd = open(device, O_RDONLY | O_NONBLOCK);

  if (fd < 0) {

    printf("Can't open device %s\n", device);

    return -1;

  }





  memset(&cgc, 0, sizeof(cgc));

  memset(&sense, 0, sizeof(sense));

  memset(&buffer, 0, sizeof(buffer));



 /* SET STREAMING command */ 

  cgc.cmd[0] = 0xb6;

 /* 28 byte parameter list length */

  cgc.cmd[10] = 28; 



  cgc.sense = &sense;

  cgc.buffer = buffer;

  cgc.buflen = sizeof(buffer);

  cgc.data_direction = CGC_DATA_WRITE;

  cgc.quiet = 1;

  

  if(speed == 0) {

/* set Restore Drive Defaults */  

    buffer[0] = 4;

  }



  buffer[8] = 0xff;

  buffer[9] = 0xff;

  buffer[10] = 0xff;

  buffer[11] = 0xff;



  rw_size = 177 * speed;



/* read size */  

  buffer[12] = (rw_size >> 24) & 0xff;

  buffer[13] = (rw_size >> 16) & 0xff;

  buffer[14] = (rw_size >>  8) & 0xff;

  buffer[15] = rw_size & 0xff;



/* read time 1 sec. */

  buffer[18] = 0x03;

  buffer[19] = 0xE8;



/* write size */

  buffer[20] = (rw_size >> 24) & 0xff;

  buffer[21] = (rw_size >> 16) & 0xff;

  buffer[22] = (rw_size >>  8) & 0xff;

  buffer[23] = rw_size & 0xff;



/* write time 1 sec. */

  buffer[26] = 0x03;

  buffer[27] = 0xE8;

 

  if (ioctl(fd, CDROM_SEND_PACKET, &cgc) != 0)      

    if (ioctl(fd, CDROM_SELECT_SPEED, speed) != 0) {

      dump_sense(cgc.cmd, cgc.sense);    

      printf("ERROR.\n");

      return -1;

    }

  printf("OK...\n");

  return 0;

}

The read/write size is the number of kb per time (which is 1 sec), so to set the read speed to 4X (or about 5.5MB/sec), the x parameter would be 32