From: s-jaschke@t-online.de (Stefan Jaschke)
Reply-To: stefan@jaschke-net.de
Organization: jaschke-net.de
To: Jens Axboe <axboe@suse.de>
Subject: Re: Problems with Toshiba SD-W2002 DVD-RAM drive (IDE)
Date: Thu, 19 Apr 2001 23:11:31 +0200
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On Thursday 19 April 2001 15:03, Jens Axboe wrote:
> On Thu, Apr 19 2001, Stefan Jaschke wrote:
> > OK. I'll check again with 2.4.4-pre4+patches:
> > (1) Mounting the SuSE DVD-ROM (-t iso9660) from /dev/hdc on /dvd and
> >     reading from /dvd works. Same for CD-ROMs. I don't have a formatted
> >     DVD-RAM.
> > (2) Reading with "dd if=/dev/hdc ..."
> >    (2.1) works with CD-ROM inserted
> >    (2.2) fails with DVD-ROM inserted
>
> dd fails with DVD-ROM inserted??? In the same way? Is this the SuSE DVD,
> and not a movie DVD? Also, check dmesg for errors.
> >    (2.3) fails with DVD-RAM inserted

"dd if=/dev/hdc of=/dev/null bs=2k count=3" produces the same strace, whether
the DVD-RAM or the SuSE DVD-ROM is inserted. I interpret the fact that the
first read() returns 0 as some lower layer coming to the conclusion that
"/dev/hdc" has length 0. 
The only line that appears in the system logs is
  "VFS: Disk change detected on device ide1(22,0)"
when I change the disks.

> > (3) Writing with "dd of=/dev/hdc ..." works (with DVD-RAM inserted).
> > (4) "mke2fs -b 2048 /dev/hdc" fails (with DVD-RAM inserted).
I took a closer look at the strace of the "mke2fs ...". The first system call
that fails is
old_mmap(NULL, 504938496, PROT_READ|PROT_WRITE, MAP_PRIVATE|MAP_ANONYMOUS, 
-1, 0) = -1 ENOMEM
It asks for 481MB, which I simply don't have. (128MB RAM,  256MB swap).
So, this may be unrelated to the kernel, just a quirk of mke2fs to ask for
that much memory.

> Could be, try
> cat /proc/ide/hdc/capacity
0                  (with empty tray)
8946816       (with single-sided 4.7GB DVD-RAM)
4875840       (with single-sided 2.6GB DVD-RAM)
9106700       (with SuSE DVD-ROM)
1325240       (with SuSE CD-ROM)

Seem to be 512 Byte blocks. Looks OK.

> And lets stick to hardware for now, ok? :-)
This means "There is hope to get the drive working under Linux"?

Correct me if I am wrong in my interpretations.

There are two mysteries (for me at least) left:
(1) Why does mke2fs need 481MB memory?
(2) Why does the very first read() on /dev/hdc return EOF?

What would you suggest to try next?

Stefan

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