SLUG Mailing List Archives
Re: [SLUG] I hate udev!
- To: slug@xxxxxxxxxxx
- Subject: Re: [SLUG] I hate udev!
- From: Ben Stanley <Ben.Stanley@xxxxxxxxxxxxxx>
- Date: Fri, 25 Nov 2005 08:09:55 +1100
The original SCSI bus specification is not designed to be hot-plugged.
You were supposed to plug it all together and then turn on the equipment
and leave it that way. Any automatic scanning was intended to be
performed at boot time. If you don't like this, then go and replace your
devices with USB ones which are intended to be hot-plugged. (I wonder if
you could get a USB <-> SCSI interface which would allow you to
'convert' an older piece of SCSI equipment to USB....)
So SCSI is not electrically designed for hot-plugging, and most pieces
of SCSI equipment come with dire warnings against doing so...
All that being said, if you don't have anything on the SCSI bus that is
continuously being used (for example, a primary system hard disk), then
it is not impossible to cause the bus to be re-scanned. I find that the
easiest way to do this is to unload the scsi driver module and then to
re-load it. For example, my SCSI host adaptor card uses the aic7xxx
driver. I have a recalcitrant scanner which seems to crash... If I need
to re-set it quite severely, I can do the following (as root):
When you run the modprobe, it scans the SCSI bus, and all the hotplug
stuff fires off and causes udev to create the necessary nodes in /dev .
So, your problems are not udev's fault, they are the fault of the
original SCSI specification, which it sounds like you have outgrown.
For myself and my SCSI problems with my recalcitrant scanner, I'm
planning to replace it with a newer model with a usb 2.0 interface. Much
easier - then my wife doesn't have to type magical incantations to
bludgeon the scanner into working!
On Thu, 2005-11-24 at 08:53 +1100, Peter Miller wrote:
> On Thu, 2005-11-24 at 06:58 +1100, prundle@xxxxxxxxxxxxxx wrote:
> > Can't see any modules that pertain to tapes.
> The module you need to reload is the lowest level one, the HBA's device
> driver. Some of them have an ioctl which rescans, so you don't need to
> rmmod insmd.
> Also, this works for my scsi slide scanner, which is usually off, too:
> echo 'scsi add-single-device <host> <channel> <id> <lun> '
> > /proc/scsi/scsi
> Read drivers/scsi/scsi.c for what else /proc/scsi/scsi can do.
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