Hi,
I understand your confusion, but if you think about it there
are some possibilities that could explain it, like:
- some little bug in st support makes it behave differently
if compiled in the kernel vs. as a module
- Gentoo devfsd.conf not properly set up for st module
loading
- Your newly compiled kernel is not the same version as the
one installed by your distro, and some bugfix occurred...
...whatever... things aren't perfect.
You didn't phrase things very clearly, and you should be
aware that it is possible to have SCSI support without
SCSI tape support, so your SCSI host adapter will enumerate
the device, but you have no driver for it in the kernel,
so you can see it in /proc but not in /dev.
At this moment, (noting that I know NOTHING about tape
drives or Gentoo, and that you omitted many important bits
from your message) the most likely to me seems that your
previous kernel did have SCSI disk, cd-rom and generic
support compiled in, but tape support only as a module,
and the module was not loaded on bootup, only later by
some script, which might not be perfect.
You should note that if you do an 'ls /dev/*' it does not
specifically ask for entry /dev/st#, therefore a LOOKUP
event does not occur, and devfsd does not load the module.
If you do 'ls /dev/st#' specifically, then you do get the
module loaded. (as much as I understand)
Hope the above is of some help,
Marton
BTW, devfs is way cool. Is there anyone though who can
help me understand what sysfs, procfs, devfs and driverfs
are intended for and what are the overlaps/differences
between them?
----- Original Message -----
From: "Brett I. Holcomb" <brettholcomb@xxxxxxxxxxx>
Date: Wed, 15 Jan 2003 18:09:43 -0500
To: devfs@xxxxxxxxxxx
Subject: SCSI Tapes and devfs
> I am new to devfs - it came with the Gentoo distribution of Linux I am
> now using. I have a Cybernetics 15 slot tape library with drive that
> has worked successfully on other distros. I'm really confused with
> devfs.
>
> I spent yesterday reading docs and working with devfs to get the thing
> working and kind of succeded - once. When I started the system I had no
> /dev/st - just /dev/sg, sd, sr. Sometime during the afternoon I did an
> ls /dev/st again and there was the st directory. Using mt I managed to
> test communciations and could talk to the tape drive under /dev/st. How
> or why the /dev/st suddenly appeared I have no idea.
>
> I shutdown the system and when I rebooted - no /dev/st anymore! My
> original kernel was built with SCSI support built in as I have an
> entirely SCSI system and did not want to mess with initrd. I could not
> get /dev/st to show up again.
>
> At that point I decided to build st support as a module and autoload it.
> Did that and there was /dev/st with my tape devices!
>
> At this point I'm confused. My understanding of devfs is that upon
> startup (Gentoo boots with devfs running) devfs will find the devices
> and create the necessary directories under /dev/. The devices ARE in
> /proc/scsi/scsi. I can see that the module loading will cause devfs to
> see a device added and create the directories. But why didn't devfs see
> the devices when st support was built into the kernel??
>
> Do I have to manually edit /etc/devfsd.conf to tell it to find my tape
> and autochanger? I thought that devfs would find them by itself.
>
> I've read man pages, the FAQ at the devfs author's site and asked on the
> Gentoo and other Linux newsgroups but am still confused. In fact the
> deafing silence on the mailing lists and newsgroups shows me not many
> people understand devfs or so it appears. Any help in unconfusing me
> would be appreciated.
>
> Thank you.
>
>
>
>
> --
>
> Brett I. Holcomb
>
>
--
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