Re: The advantage of modules?

[Michael Meissner <meissner@spectacle-pond.org>]

On Mon, Jan 08, 2001 at 07:26:01PM +0100, Ookhoi wrote:
> >    3)	Having drivers as modules means that you can remove them and
> >    reload them.  When I was working in an office, I had one scsi
> >    controller that was a different brand (Adaptec) than the main scsi
> >    controller (TekRam), and I hung a disk in a removable chasis on the
> >    scsi chain in addition to a tape driver and cd-rom.  When I was
> >    about to go home, I would copy all of the data to the disk, unmount
> >    it, and then unload the scsi device driver.  I would take the disk
> >    out, and reload the scsi device driver to get the tape/cd-rom.  I
> >    would then take the disk to my home computer.  I would reverse the
> >    process when I came in the morning.
> 
> You don't need modules for this to work.

Quoting from drivers/scsi/scsi.c:

	/*
	 * Usage: echo "scsi add-single-device 0 1 2 3" >/proc/scsi/scsi
	 * with  "0 1 2 3" replaced by your "Host Channel Id Lun".
	 * Consider this feature BETA.
	 *     CAUTION: This is not for hotplugging your peripherals. As
	 *     SCSI was not designed for this you could damage your
	 *     hardware !
	 * However perhaps it is legal to switch on an
	 * already connected device. It is perhaps not
	 * guaranteed this device doesn't corrupt an ongoing data transfer.
	 */

so my take is unless you explicitly use hotplug devices (I wasn't), that it is
much safer to unload the driver, unattach/attach scsi devices, and then reload
the driver (which will scan the scsi bus for devices), which you need modules
for.

-- 
Michael Meissner, Red Hat, Inc.  (GCC group)
PMB 198, 174 Littleton Road #3, Westford, Massachusetts 01886, USA
Work:	  meissner@redhat.com		phone: +1 978-486-9304
Non-work: meissner@spectacle-pond.org	fax:   +1 978-692-4482
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