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

[Alan Cox]

On Thu, Nov 18, 2004 at 12:21:29PM -0500, David Zeuthen wrote:
> I'm curious why BLKGETSIZE64 ioctl() then succeeds and give me the size
> if you say it's bogus? Care to explain the 4096 byte difference?

We ask the drive it reports an answer. That answer is not precise

> [1] : Exactly what media does this apply to? All non DVD-ROM and CD-ROM?

CD-R and CD-RW. I don't know enough about DVD formats to answer on those.

> e.g. /sys/block/hdc/hdc%d for the various partitions and sessions
> (assuming hdc is an optical IDE drive)? I guess the kernel could safely
> give the right size of /sys/block/hdc/hdc1. With that it would be a lot

The kernel can guess the size of partitions if the partition table 
gives sizes. 

> easier to support e.g. PhotoCD discs (which are multisession). FWIW,
> that's what Darwin does.

Multisession is not the same as partitioned. We do support mounting other
sessions but as a mount option. We don't cleanly handle partitioned CD
which is unfortunate for HFS stuff.

Alan