Re: Pioneer 6-CD changer (DRM-6324X)

Jim Weisenbach wrote:
[snip discussion of a CD-changer that uses multiple LUNs]
After doing the above 'echo' steps the new proc file showed all 6 LUNs
then the 'hardware browser' showed all 6 as separate devices (scd0-scd5) and pushed the IDE cdrom down from scd1 to scd6. (During this browse each of the trays was loaded and unloaded - fairly time consuming process with each disk getting spun up and read. I can live with that since it would happen once at bootup.) No problem so far...

Good.

I then edited fstab to create the new mount instructions, with new
sub-directories in /mnt, for each of these devices and rebooted...

Good.

Alas, the entries in /proc/scsi/scsi don't 'stick' because I was left with
only two of the 7 mounts in fstab and /proc/scsi/scsi was back to the
original data - two devices.

That's to be expected. You'll have to do the echo stuff each time you
reboot.

So... I'm guessing that the phrase 'probe all LUNs' is a vital, missing link, yes?

You either need to do the echo part each time you reboot -or- enable the
"probe all LUNs" option in the kernel. But not both.

I looked at the BIOS startup menus for the controller (BusLogic BT946C) but nothing indicated any options for LUNs at that level.

The "probe all LUNs" option is a kernel option, nothing to do with the
SCSI BIOS.

I learned elsewhere that LILO/GRUB can be used to insert special commands and wondered about 'max_luns=x' - would this accomplish the same thing. I couldn't really find out much more detail on this option.

The "max_luns" is (I believe) used simply to limit the number of LUNs
probed by the "Probe all LUNs" option. IOW, I don't think it works
without the kernel option set.

I've also read about loadable modules... is there anything that I should
spend time in that area,

No, the probing is not a loadable module.

or is this going to involve a rebuilding of the
kernal (something I've never done...yet)?

Yes, you'll have to rebuild the kernel. Somebody else can probably give
you distro-specific advice for Fedora. There is also a Kernel-HOWTO at
http://www.tldp.org/ that should help.

The important part is when configuring the kernel (with 'make
menuconfig', for example) to select "Device Drivers" -> "SCSI Device
Support" -> "Probe all LUNs on each SCSI device".

One other idea I had (I seem to know just enough to be dangerous to myself <grin>) related to someone's comment about a script. If the previous echo steps were put in a script, would they be accessed before fstab? I don't have the foggiest idea of what I'm getting into in this direction, but it sounded good in my mind! :)

You'd have to either put the echo part in a script that was run before
/etc/fstab is read -or- make sure that fstab specifies the 'noauto'
option for them. That way, they won't be mounted at boot time but you
can mount them on-demand. For example:

/dev/scd0 /mnt/slot1 auto user,noauto,ro 0 0

Note the "auto" in the fstype field and the "user,noauto" fields in the
option field. These are important, and allow any user (not just root)
to mount the drives.

You'll either have to go the "noauto" route and put the echo commands in
/etc/init.d/rc.local (or whatever your distro calls it) -or- rebuild the
kernel. (Building your own kernel isn't hard---just a little
intimidating---if you just make the one change for probing all LUNs.
It's when you start messing around with other settings that things can
get more interesting. Work your way up to that!)

And one final possiblity - I have a set of disks for Fedora Core 3 (will have to change the IDE cdrom to a dvd drive and that's the main reason - just lazy - that I haven't upgraded). But if I did, do I have the option of getting the kernal configured during the installation?

You'll have to build your own kernel, if you want to enable "Probe all LUNs", regardless of which distribution you use. Distribution kernels don't enable probing all LUNs since it breaks some (defective) hardware.
.

Relevant Pages

  • Re: aic7xxx und SuSE 10.0
    ... Dann ist die Ursache vermutlich einfach ein Kernel der nicht alle LUNs ... Aber der erste Beitrag von Claus hat geholfen. ...
    (de.comp.os.unix.linux.hardware)
  • Re: Data Router and MSL5026 Library
    ... > Adam Price wrote: ... I have been able to compile with the 'probe all scsi ... Are you sure you are running from a kernel ... make menuconfig (select the option to probe all scsi luns) ...
    (comp.unix.admin)
  • Re: Pioneer 6-CD changer (DRM-6324X)
    ... John-Paul Stewart wrote: ... the Pioneer unit in question *is* a SCSI CD-ROM ... changer and uses multiple LUNs, so the above suggestion sounds right. ... OP will likely need to build a kernel with the option ...
    (comp.os.linux.hardware)
  • Re: How to change max scsi partitions ?
    ... Random guess, the partitions are not the problem, but you are ... using more LUNs then the kernel is probing for per default, ...
    (comp.os.linux.hardware)