Re: LANANA: To Pending Device Number Registrants

H. Peter Anvin
2001-05-16T23:56:12Z

Richard Gooch wrote:
>
> OK. How do you figure on dealing with the problem of multiple
> high-level drivers talking to the same device? How does sr.o "know"
> that this is also a CD-RW? How does sg.o "know" that this is also a
> tape?
>

At some point something talks to the device -- in this case, it's the
SCSI layer. Follow the interfaces in the kernel and it becomes obvious.

> Where does the responsibility lie for figuring out the capabilities?
>
> Further, which device node/fs/driver exports the capability list?
>
> And what about locking between drivers?

Orthogonal issue. You may want a locking mechanism, but it almost
certainly should not be automatic.

Note that especially ide-scsi is a good example on how *not* to do
things. The fact that you have to choose one of two interfaces for
different operations (I can't use a CD-writer in the default
configuration!) is insane.

-hpa

--
<hpa@transmeta.com> at work, <hpa@zytor.com> in private!
"Unix gives you enough rope to shoot yourself in the foot."