LinuxQuestions.org - How to force a CDROM drive to re-scan a disc

I wrote a small C program that uses ioctls to determine the drive status and disc status of the cd-rom drive on my Debian Etch laptop. The problem is that after every reboot or power cycle, I have to eject and re-insert the disc. If I don't do this, the drive still seems to see the disc, but doesn't have information about the data scheme of the disc and can't do anything with it until re-insertion.

Is there any way to force the cd drive to re-scan the disc without ejecting the cd tray?

Program source:

Code:

#define CDDEVICE "/dev/cdrom" // CDROM device

int cd_drive_status(int cd_drive_fd);

int cd_drive_disc_status(int cd_drive_fd);

int cd_drive_reset(int cd_drive_fd);





int main(int argc,char **argv)

{

int cd_drive_fd=-999; // CDROM device file descriptor



// open the cd drive

if ((cd_drive_fd = open(CDDEVICE,O_RDONLY | O_NONBLOCK)) < 0) {

perror("open");

exit(1);

}



cd_drive_reset(cd_drive_fd); printf("\n");

cd_drive_status(cd_drive_fd); printf("\n");

cd_drive_disc_status(cd_drive_fd); printf("\n");



close(cd_drive_fd);

return 0;

}





////////////////////////////////////////////////////////////////////////////////

////////////////////////////////////////////////////////////////////////////////

int cd_drive_reset(int cd_drive_fd){

int retVal=-999;

retVal=ioctl(cd_drive_fd, CDROMRESET, NULL);

printf("Resetting CDROM: %d - %s\n", retVal, strerror(retVal));

return retVal;

}





int cd_drive_status(int cd_drive_fd){

int retVal;

retVal=ioctl(cd_drive_fd, CDROM_DRIVE_STATUS, 0);

printf("CDROM Drive Status: %d - ", retVal);

switch(retVal){

#define PRINT_AND_BREAK( a ) printf( a ); break // Gotta love the MACRO's Smile

case CDS_NO_INFO: PRINT_AND_BREAK("CDS_NO_INFO\n");

case CDS_NO_DISC: PRINT_AND_BREAK("CDS_NO_DISC\n");

case CDS_TRAY_OPEN: PRINT_AND_BREAK("CDS_TRAY_OPEN\n");

case CDS_DRIVE_NOT_READY: PRINT_AND_BREAK("CDS_DRIVE_NOT_READY\n");

case CDS_DISC_OK: PRINT_AND_BREAK("CDS_DISC_OK\n");

case -1: PRINT_AND_BREAK("ioctl function error\n");

// case ENOSYS: PRINT_AND_BREAK("Drive can't detect drive status\n");

// case EINVAL: PRINT_AND_BREAK("Slot number beyond capacity of drive\n");

// case ENOMEM: PRINT_AND_BREAK("Insufficient memory\n");

}

return retVal;

}





int cd_drive_disc_status(int cd_drive_fd){

int retVal=-999;



retVal=ioctl(cd_drive_fd, CDROM_DISC_STATUS, 0);

printf("CDROM Drive Disc Status: %d - ", retVal);

switch(retVal){

#define CASE_PRINT( value , string )\

case value:\

printf("%s\n", string);\

break;

CASE_PRINT(CDS_NO_INFO, "CDS_NO_INFO");

CASE_PRINT(CDS_NO_DISC, "CDS_NO_DISC");

CASE_PRINT(CDS_TRAY_OPEN, "CDS_TRAY_OPEN");

CASE_PRINT(CDS_DRIVE_NOT_READY, "CDS_DRIVE_NOT_READY");

CASE_PRINT(CDS_DISC_OK, "CDS_DISC_OK");

CASE_PRINT(CDS_AUDIO, "CDS_AUDIO");

CASE_PRINT(CDS_DATA_1, "CDS_DATA_1");

CASE_PRINT(CDS_DATA_2, "CDS_DATA_2");

CASE_PRINT(CDS_XA_2_1, "CDS_XA_2_1");

CASE_PRINT(CDS_XA_2_2, "CDS_XA_2_2");

CASE_PRINT(CDS_MIXED, "CDS_MIXED");

default:

printf("unknown\n");

break;

}

return retVal;

}

Program output after reset:

Code:

Resetting CDROM: 0 - Success



CDROM Drive Status: 4 - CDS_DISC_OK



CDROM Drive Disc Status: 0 - CDS_NO_INFO

(dmesg also contains the following line:
"cdrom: This disc doesn't have any tracks I recognize!")

Program output after re-inserting disc:

Code:

Resetting CDROM: 0 - Success



CDROM Drive Status: 4 - CDS_DISC_OK



CDROM Drive Disc Status: 101 - CDS_DATA_1

Any help is greatly appreciated.

-Aaron