Re: Multi-session CD-ROM

emoenke (
Wed, 28 Jun 1995 20:08:59 +0200 (MET DST)

Hi, wrote:

>Subject: Multi-session CD-ROM

>I got a Kodak Photo CD a while ago. I got hpcdtoppm and xpcd, and everything
>worked beautifully. Then I took the CD-ROM back in, and added some more
>pictures to it. When I brought it home, much to my surprise, the disk
>appeared to Linux as though nothing had changed. An "ls -l" command
>indicated that not only had no new pictures been added, but the date stamps
>on all files were the date when the CD-ROM was initially created.

You simply got access to the first session only.

>I've learned enough about what's going on here to know that when a CD-ROM
>is updated, another "session" is created. I've taken a brief look at the
>code in the "iso" directory in the Linux kernel source. It looks as though
>the multiple session problem was addressed by someone, but it isn't
>working yet.

It IS working. The isofs routines ask the driver for an offset value,
needed to access the most recent "volume descriptor" instead the first.
The IOCTL "CDROMMULTISESSION" is defined for this, and used.
Unfortunately, the Linux CDROM driver writer brigade seems less interested
in fulfilling these things - they simply let their drivers return an error
instead of submitting a value.
sbpcd (with the CR-56x, the Longshine LCS-7260, the TEAC CD-55A and
hopefully with the CD200 drives), sr (with some "well-known" Toshiba, NEC
and Sony drives) and - with one of the next 1.3 patches - cm206 (Philips)
and mcdx (at least with the Mitsumi FX001 non-ATAPI drives) are able to
point to "the last" session, and cdu31a hopefully does it, too, but still
a non-standard way.

Someone should start an action "a PhotoCD donation for each Linux CDROM
driver writer": two sessions - the first with some pictures like
"Linus himself, preparing for midsummer night", and the second session
announced like "Linus himself, declaring the essence of midsummer night
to his groupies". This could enable some spirit for the next step. ;-)

Cheers -e-

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