Subject: Re: Disklabel oddity
To: Wolfgang Solfrank <>
From: Ken Hornstein <>
List: tech-kern
Date: 04/19/1996 14:14:45
>> Hmmm, the more I think about it, the more I realize that using disklabel
>> perhaps isn't the right thing to do.  The block numbers in the ISO filesystem
>> are probably absolute, and shouldn't be offset-corrected by the disklabel
>> routine.
>That's correct. (At least it should. I can imagine people writing something
>different on their CDs. In fact, thinking about it again, I'd not be surprised
>if those "multi-volume" CDs do have relative addresses instead of absolute

So, I don't suppose there is a way to differentiate betweeen a multisession
and a faux-multivolume CD-ROM, is there?

>> It almost sounds like it makes more sense to add functionality to
>> mount_cd9660 so you could specifiy a session number.  You could then have
>> it read the disklabel, figure out the start of the ISO filesystem, and pass
>> that to the mount system call.  What do people think of that idea?
>What disklabel are you referring to?

Sorry, I was EDRUNK last night, and I'm not quite all there today :-)  I'm
talking about the TOC on the disk.

>It should request the start of the requested session from the driver, read
>the volume labels (block 16 and following) from there, and use the block
>numbers given as absolute addresses on the CD. By default, it should use
>the last session (requested by another ioctl).

Okay, here's where I get a bit confused.  The TOC on the disk shows a bunch
of data tracks.  Are the data tracks different from the sessions, or are
they one-in-the-same?  Are sessions a layer above data tracks?  Will a
3-session CD-ROM show 3 data tracks?

If you have any place where this is all explained, please point me to it!
I've been digging around lately, but I haven't found much info about
sessions yet.