Re: PCI device driver vs SCSI device driver

From: Josef Möllers (josef.moellers_at_fujitsu-siemens.com)
Date: 03/16/04 

Date: Tue, 16 Mar 2004 08:58:22 +0100

tcs wrote:

> Can you show me some links to sources where PCI/SCSI drivers reside in
> the the driver? Or, this sentence is ill framed. If you get what I mean,
> please show me where to find related sources.

If we add your question about PCI vs SCSI, then:
you're talking about three different levels. Simply speaking:

PCI is the thingy where you plug SCSI host adapters (the whitish slots
on the motherboard) There are motherboards which support hotplugging on
the PCI bus. It requires powering down the PCI slot as well as isolating
the entire slot from the PCI bus.

SCSI is the bus which comes out of the SCSI host adapter. Although not
standardized (AFAIK), you can often hotplug SCSI devices (e.g. hard disk
drives) and this is used by most if not all SCSI-RAID controllers to
implement hotswappable devices (if a drive fails, the controller
replaces it by another, spare drive, and the broken drive can be
extracted and replaced by a new drive without stopping the system or
halting the RAID subsystem. The controller will (autonomously or with
manual intervention) detect the replacement and mark the new drive as
spare). The SCSI bus is pretty robust and the SCSI protocol is capable
of handling short interruptions on the bus.

E.g. a floppy drive, an MO disk, a CDROM drive attached to the SCSI bus
are removable media. While the drives themselves stay on the SCSI bus
(and continue to respond to SCSI commands), the media can be removed and
inserted more or less at will and the drives will respond with
appropriate status messages.

HTH,

Josef 

-- 
Josef Möllers (Pinguinpfleger bei FSC)
	If failure had no penalty success would not be a prize
						-- T.  Pratchett

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