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linuxscsi

CDROM function - where does the function pointer go to?

I am trying to debug an issue where the standard linux CDROMEJECT returns an error even though the disk ejected.

Standard eject command used.

ioctl(FP,CDROMEJECT)

When I look at the cdrom.c I can see the eject function and the errors (e.g: http://lxr.free-electrons.com/source/drivers/cdrom/cdrom.c#L2303). I am fine with where error codes are returned but you also have lines like this:

cdi->ops->lock_door(cdi, 0)

Now lock_door is a function pointer (see header file here). My issue is I cannot for the life-of-me figure out which function the lock_door pointer points to! I would expect this to point to a function that then sends a SCSI command to the CD/DVD drive.

I suspect I am missing some fundamental but really not sure what! Any idea where I find where the function pointers in struct cdrom_device_ops point to?

Solution

  • If you do an LXR "Freetext Search" for ".lock_door" you can see it being set for the scsi driver here and if you click on sr_lock_door you find it defined in sr_ioctl.c:

    int sr_lock_door(struct cdrom_device_info *cdi, int lock) {
        Scsi_CD *cd = cdi->handle;
        return scsi_set_medium_removal(cd->device, lock ?
                       SCSI_REMOVAL_PREVENT : SCSI_REMOVAL_ALLOW);
}