can't read raw CD device

[Incoming Mail List]

Hello,

I'm trying to understand why I cannot read my CD drive directly from a 
'c' program using the read(2) system call, or even using the dd(1)
command.  As you will see, I have both the acd0 and cd0 devices since
I have atapicam configured in the kernel.

I can mount cdrom media using mount() and access data via the cd9660
file system, so I know the drive and the media are not the problem.

#dd if=/dev/acd0 of=/dev/null count=20
dd: /dev/acd0: Invalid argument
0+0 records in
0+0 records out
0 bytes transferred in 0.000163 secs (0 bytes/sec)

#dd if=/dev/cd0 of=/dev/null count=20
dd: /dev/cd0: Invalid argument
0+0 records in
0+0 records out
0 bytes transferred in 0.000179 secs (0 bytes/sec)

Thanks,
Jon