[stgt] tgt and DVD

FUJITA Tomonori fujita.tomonori at lab.ntt.co.jp
Fri Sep 25 02:03:29 CEST 2009

On Thu, 24 Sep 2009 15:17:25 +1000
ronnie sahlberg <ronniesahlberg at gmail.com> wrote:

> >> Frustration: The dvd/cd iso feature appears to work with 'simple' CD's only.
> >> More advanced UDF or multi-session CDs (like recent Distributions of
> >> Microsoft OS/Development tools) appear to not be supported.
> >
> > I'm not familiar with this area so I CC'ed Ronnie Sahlberg, who wrote
> > that part.
> >
> That is true. The current implementation only emulates single-session disks.
> It does support writeable single-session disks, i.e. that you can
> "burn" one of these DVD's but
> I never implemented multi-session.
> > BTW, you can't do that even with IET, right?
> That is true. IET only supported single-session disks as well. I.e.
> plain ISO images.

Thanks for the explanation.

> I do think it would be worth it to eventually replace mmc.c with cdemu
> but it would be nice to do so without losing functionality.

Yeah, agreed. losing the existing functionality is not nice.

> I think it would be quite a lot of work  but worthwhile
> 1, add emulation of writing to a dvd to cdemu. This is not that very
> hard, at least if you only aim to support to burning to single-session
> dvds.
> 2, should probably work with the cdemu people and break
> cdemud-device.c out into a separate link library that tgtd could link
> to.
> (maybe keep mmc.c still around as a last resort and use it if
> cdemud-device.a is not available?)
> 3, rework the public api in cdemud-device.c to remove exposing the
> glib/dbus dependencies and make the exposed api only use posix types.
> (I think one very attractive feature of the tgtd codebase is that it
> has so few dependencies on headers from other packages)
> 1 is only important if we want to keep the "tgtd can burn to emulated
> blank disks" feature.
> 2 would open up code sharing and reuse between cdemu and tgtd, and
> other projects that want to access a scsi mmc emulation library.
> 3 is only my personal view. I really like that tgtd does not depend on
> glib or other external packages.

Yeah, agreed. cdemu is released under GPL. I prefer just exploiting
(or stealing) their code.

I have no time to work on multi-session support but patches are very

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