Re: CD-RW & DVD-RAM

Rogier Wolff (R.E.Wolff@BitWizard.nl)
Sat, 29 May 1999 18:46:12 +0200 (MEST)


Cameron Simpson wrote:
> On 24 May 1999, in message <374939B2.D284993F@guideguide.com>
> Christof Damian <cdamian@guideguide.com> wrote:
> | Ben Fennema wrote:
> | > But the fs is just one part of writing the a CD-RW.
> | > Support for packet writing has to be added to the cdrom driver (or
> | > something).
> | >
> | > Otherwise pulling the same stunt as people have been doing for
> | > DVD-RAM is possible, but you only get 83 meg on a disc.
> | > (Formating a disc with 1 block/packet).
> |
> | Which stunt ist that ? How are DVD-RAMs supported by linux at the
> | moment ?

Christof, Could you try my patch? I'd like afew people with
CD-RW to try them.

It is reachable from

http://www.bitwizard.nl/dvd/

You will have to look at how your CD-RW is detected and add some info
about it to the table in scsi.c .

> - most DVD-RAMs, instead of appearing as two SCSI LUNs, one
> a CD-ROM and one a rewritable removable drive, appear
> as one device; there're a few patchs floating about to make
> the kernel recognise the vendor strings and make two entries.
> I am using this approach happily with a Creative DVD-RAM.

With the patch, and with the "two-lun" approach I think that there
still is an issue with caching.

In either case, the system might be caching say sr0/block1234 then
write sda/block1234 which might invalidate the cache of sr0/block1234,
as they refer to the same physical disk block.

The Matshushita (sp?) DVD RAM drives have a software selectable switch
(non-volatile!) wether or not they will present themselves as two-lun
or not. We have the specs, and are working on a Linux-userland tool
to view/set that switch.

Roger.

-- 
** R.E.Wolff@BitWizard.nl ** http://www.BitWizard.nl/ ** +31-15-2137555 **
*-- BitWizard writes Linux device drivers for any device you may have! --*
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