I'm having trouble on my unstable (knoppix 3.2 installed to HD) system & haven't found a solution in the forum. The original system installed to HD recognizes the CD player fine. When I compile my own kernel (2.4.22, 2.4.24 or 2.6, with SCSI & SCSI generic support ), I'm getting a "/dev/cdrom is not a valid block device" error. Here's the relevant output from dmesg:
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hdd: CD-224E, ATAPI CD/DVD-ROM drive
ide-cd: passing drive hdd to ide-scsi emulation.
hdd: attached ide-scsi driver.
SCSI subsystem driver Revision: 1.00
scsi0 : SCSI host adapter emulation for IDE ATAPI devices
Vendor: TEAC Model: CD-224E Rev: K.0B
Type: CD-ROM ANSI SCSI revision: 02
=========================================

... but no joy. When I boot my original kernel (the original that was installed to HD), the cdrom attaches fine. Here's dmesg from that boot, after HDD was passed to ide-scsi:

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SCSI subsystem driver Revision: 1.00
SCSI host adapter emulation for IDE ATAPI devices
Vendor: TEAC Model: CD-224E Rev: K.0B
Type: CD-ROM ANSI SCSI revision: 02
Attached scsi CD-ROM sr0 at scsi0, channel 0, id 0, lun 0
sr0: scsi3-mmc drive: 24x/24x xa/form2 cdda tray
Uniform CD-ROM driver Revision: 3.12
========================================

Looks like what's missing in the first instance is the last three lines. Even I can figure out it's using sr0. In /dev, sr0 is symlinked to sda1.
When I use cdrecord --scanbus to see if the problem system is even seeing the cd player, I get an encouraging response:

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Linux sg driver version: 3.1.25
Using libscg version 'schily-0.8'.
scsibus0:
0,0,0 0) 'TEAC ' 'CD-224E ' 'K.0B' Removable CD-ROM
===============================================

I'm stumped ... /dev/cdrom is a symlink to scd0. sr0 is also a symlink to scd0. At boot HDD, the cd player, is getting passed to the ide-scsi driver, sg is being utilized I've tried mounting /dev/sda1, /dev/scd0, /dev/sr0. The only way I can get the thing to show up is to boot my original kernel, Knoppix installed to the hard disc, which isn't great because my compiled kernel otherwise is rockin'. I know I'm letting my frustration get in the way & I'm missing something really basic, so any help would be appreciated. Did I overlook a compilation option?