Re: SCSI host numbers?

From: Richard Gooch (
Date: Wed Jan 02 2002 - 14:31:01 EST

Alan Cox writes:
> > Under some scenarios Linux assigns the same
> > host_no to more than one scsi device.
> >
> > Can someone tell me what is the intended behavior?
> A number should never be reissued.
> > The problem is that a newly registered device gets
> > its host_no from max_scsi_host. max_scsi_host is
> > decremented when a device driver is unregistered
> > (see drivers/scsi/host.c) allowing a second new
> > host to reuse the same host_no.
> I guess it needs to either only decrement the count if we are the
> highest one (trivial hack) or scan for a free number/keep a free
> bitmap. The devfs code has a handy little unique_id function for
> that

Yeah, I was going to get around to submitting a patch to change the
SCSI host allocation code to use devfs_alloc_unique_number(), but
right now that function is only functional if CONFIG_DEVFS_FS=y
(otherwise you get a stub function which returns -1). So really this
should be turned into a generic function, which was my plan all along,
but I didn't want to fight that battle back then. Now that it's in
the tree, I can look at doing this.

Comments? Got a suggestion for which file the generic function should
go into? I figure on stripping the leading "devfs_" part of the
function names.


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