more information on my trouble reading CDROM's with hdc=ide-cd. Anybody else?

[Paul Johnson]

I asked about this before in here and got some good hints.  I still 
can't mount cdr's I've written on my Inspiron 8600 laptop with the NEC 
ND-5100a CD/DVD+RW.  The symptom is that CDRs won't mount and the output 
to /var/log/messages says the disk is timing out:

kernel: hdc: irq timeout: status=0xd0 { Busy }
kernel: hdc: irq timeout: error=0xd0LastFailedSense 0x0d
kernel: hdc: DMA disabled
kernel: hdc: ATAPI reset complete

I've been reading everywhere about cdrom/dvd problems in linux.  I note 
that this error has been observed now and then since 1998, and there's 
never a very good explanation of what's wrong.  Some people suspect 
hardware failure.  I have made bug reports, first to the redhat bugzilla:

http://bugzilla.kernel.org/show_bug.cgi?id=3755

And then last night to the kernel.org itself.

http://bugzilla.kernel.org/show_bug.cgi?id=3755

The important new information is that when starting with no kernel 
option or with hdc=ide-cd, I CAN mount cdrom's printed at the factory 
(Microsoft, for example), but cannot mount CDRs that I write.  I found 
at least one bug reporter who contended that the way Fedora core 2 
writes the "last part" of a CDR is not managed well by the ide-cd 
module.  On the other hand, ide-scsi can mount either kind of disk.

Before I found that ide-scsi would cause disks to be mounted, I was 
thinking the problem was in the CD-DVD+RW device itself.  People have 
contended to me that when you lose the ability to read CDRs, it is a 
signal that your laser is getting weak, because the CDRs you make 
yourself are not so sharp and clear as the one the factory makes with 
its high quality writers.  There may still be some truth in that, but I 
think that if it really was the cause of trouble, then setting 
hdc=ide-scsi would not help.

It seems to me the problem has to be in the ide-cd support.  This bug 
report on kernel.org suggests as much, but I do not know if the author 
is correct or not:

http://bugzilla.kernel.org/show_bug.cgi?id=3362

Here's what I don't understand: If there is some bug in CD reading, why 
doesn't it affect all Linux systems.  Why just a few of us?


-- 
Paul E. Johnson                       email: pauljohn at ku.edu
Dept. of Political Science            http://lark.cc.ku.edu/~pauljohn
1541 Lilac Lane, Rm 504
University of Kansas                  Office: (785) 864-9086
Lawrence, Kansas 66044-3177           FAX: (785) 864-5700