Linux-kernel mailing list archive 1999-41,: Re: scsi disk detection and /dev names, RE: My $.02 on the raging

# Re: scsi disk detection and /dev names, RE: My $.02 on the raging

H. Peter Anvin (hpa@transmeta.com)
11 Oct 1999 21:03:57 GMT

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Followup to: <Pine.LNX.4.05.9910111303560.29538-100000@ns.snowman.net>
By author: Stephen Frost <sfrost@ns.snowman.net>
In newsgroup: linux.dev.kernel
>
> On Mon, 11 Oct 1999, Jakma, Paul wrote:
>
> > So devfs is a quick workaround of this limitation rather than being a real
> > cure (for this particular prob). If anyone with the coding skills is
> > listening, it'd be great if static /dev could support location based disk
> > names too.
>
> As a thought, one thing I was thinking of is, if you have a list of
> what devices are in a system by major,minor, if there was then a way to
> query information about that device you could then have a user-space proggy
> create the location-based device names for you...
> Of course, this does cause some issue when you wonder about the
> problems of a major,minor pairs being reused... Hadn't thought about that
> one much yet. ;)
>

This is correct; the program "scsidev" by Eric Youngdale has done this
for a long time, for example.

A few more things to remember when you're talking about
"location-based names":

1. PCI bus numbers are fairly volatile; they are assigned sequentially
by a depth-first search. Inserting a multiport Ethernet card
(which usually have PCI-PCI bridges onboard) could move a whole lot
of bus numbers for you. Same thing with SCSI controller numbers.

2. Consider if location-basis is really what you want, and if so, if
it really matters. Rearranging your SCSI busses, for example, is
probably quite common. On busses where you have device serial
numbers, or for disks where you have labels, it probably would
provide a better basis.

3. Solaris seems to teach the lesson that if you make the device names
too complex, noone will use them. Solaris has a very complete
location-based device naming scheme, but I know very few Solaris
administrators who use those names, as opposed to the short
symlinks.

-hpa

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