I believe that you are experiencing the difference between using the IDE drivers vs. SCSI emulation. When the CDROM/DVD is mapped to /dev/sr0 you are using the SCSI emulation drivers to access the device. When you don't use SCSI emulation then the device will (probably) be mapped to /dev/hd? where the ? is an alphabetic character such as a, or b, or c. So you may find that your CDROM/DVD is mapped to /dev/hdc, for example. You can look around in the proc file system to see if you can find the mapping of the CDROM/DVD. Here is how I can see my CDROM/DVD in the /proc file system.
Code:
root> ls /proc/ide
drivers hda hdb hdc hdd ide0 ide1
root> ls -l /proc/ide
total 4
-r--r--r-- 1 root root 0 Sep 27 14:03 drivers
lrwxrwxrwx 1 root root 8 Sep 27 14:03 hda -> ide0/hda
lrwxrwxrwx 1 root root 8 Sep 27 14:03 hdb -> ide0/hdb
lrwxrwxrwx 1 root root 8 Sep 27 14:03 hdc -> ide1/hdc
lrwxrwxrwx 1 root root 8 Sep 27 14:03 hdd -> ide1/hdd
dr-xr-xr-x 4 root root 0 Sep 27 14:03 ide0
dr-xr-xr-x 4 root root 0 Sep 27 14:03 ide1
root> ls -l /proc/ide/ide1
total 0
-r--r--r-- 1 root root 0 Sep 27 14:04 channel
dr-xr-xr-x 2 root root 0 Sep 27 14:04 hdc
dr-xr-xr-x 2 root root 0 Sep 27 14:04 hdd
-r--r--r-- 1 root root 0 Sep 27 14:04 mate
-r--r--r-- 1 root root 0 Sep 27 14:04 model
root> ls -l /proc/ide/ide1/hdc
total 0
-r--r--r-- 1 root root 0 Sep 27 14:04 capacity
-r--r--r-- 1 root root 0 Sep 27 14:04 driver
-r-------- 1 root root 0 Sep 27 14:04 identify
-r--r--r-- 1 root root 0 Sep 27 14:04 media
-r--r--r-- 1 root root 0 Sep 27 14:04 model
-rw------- 1 root root 0 Sep 27 14:04 settings
root> cat /proc/ide/ide1/hdc/model
SONY DVD RW DRU-500A
root>
