SOLVED: autoloading sg driver during boot

[Aleksandar Milivojevic]

Aleksandar Milivojevic wrote:
> Probably something trivial, but can't seem to find solution (other than 
> placing "modprobe sg" in /etc/rc.local).
> 
> I attempted something like this in modprobe.conf:
> 
> alias char-major-21 sg
> 
> (and also char-major-21-* variant)
> 
> The problem is, there are no /dev/sg* entries in /dev when machine 
> boots.  They are created by udev when "sg" driver loads.  Chicken and 
> egg problem.  Kind of.  So the above lien in modprobe.conf does not 
> really work.
> 
> So....  the question is, is there any way to instruct udev to create 
> /dev/sg* nodes (so that applications can access it and trigger auto 
> loading of sg driver)?  Or instruct system to autoload sg module during 
> boot if there are any SCSI devices, which would trigger udev to create 
> /dev/sg* nodes?  Other than placing "modprobe sg" in /etc/rc.local.

Problem solved.  In short, I had a buggy version of hotplug package 
installed.

The fix is simple.  What needs to be done is to edit 
/etc/hotplug/scsi.agent script.  It checks the device type and loads 
appropriate driver.  The stock Fedora script does not load any drivers 
for type 8 (changer) device, and the one I have (taken from RHEL 4) had 
a typo in the line for changer device.

Near the end of the script is a case statement that selects appropriate 
driver depending on numeric SCSI device type (as return by device when 
it is queried).  The stock Fedora script has a line for changer device 
empty (does not load any driver):

    8)          TYPE=changer ;;

And the script from RHEL 4 has a typo (note misspelled word moudle -> 
module):

    8)          TYPE=changer ; MOUDLE = sg ;;

It should read:

    8)          TYPE=changer ; MODULE = sg ;;

As soon as I fixed it, everything works OK, and sg module is 
automatically loaded during boot (by hotplug subsystem), and udev 
creates appropriate device nodes automagically (as it is supposed to 
do).  Weehee...

-- 
Aleksandar Milivojevic <amilivojevic at pbl.ca>    Pollard Banknote Limited
Systems Administrator                           1499 Buffalo Place
Tel: (204) 474-2323 ext 276                     Winnipeg, MB  R3T 1L7