Re: Manual udev invocation & via hotplug method gives different results

[Patrick Mansfield <patmans@us.ibm.com>]

On Fri, Mar 12, 2004 at 10:44:35AM -0800, Sabharwal, Atul wrote:
> >>Have you tried using udevtest to see if that gives you the same
> result?
> 
> I tried udevtest and it gives same result as udev. The scsi
> commands give three device entries. 

Getting an sda, sda1, and sg1 is the expected behaviour. sg is the "scsi
generic" or scsi pass through interface and ... sda1 a partition of sda.

If you were getting multiple entries in /sys/bus/scsi/devices for the one
command, that would be bad.

The addition and removal of a scsi device using /proc/scsi/scsi (or sysfs
interfaces for a single LUN) is the equivalent of a hotplug removal and
addition of a single scsi device (LUN or disk, not a host and not a scsi
target). These are vary useful for testing udev or other hotplug code,
they can be used with USB mass storage devies and scsi_debug disks.

Also, you can use the sysfs remove/scan interfaces. The /proc ones will go
away someday. The scan interface is nicer for multi-LUN devices as it will
use the REPORT LUNS to scan, and can scan an entire bus, target or just a
single LUN.

To remove a LUN use:

	echo anythinghere > /sys/bus/scsi/devices/H:C:T:L/delete

To scan, general syntax is:

	echo "C T L" > /sys/class/scsi_host/hostH/scan

Where H C T L are respectively the host number, channel, target id, and
lun.

So remove a single LUN at 1 0 0 0 via:

	echo anythinghere > /sys/bus/scsi/devices/1:0:0:0/delete

The scan can be wildcarded via '-'.

To scan all of host1:

	echo "- - -" > /sys/class/scsi_host/host1/scan

Scan a single channel/bus 0:

	echo "0 - -" > /sys/class/scsi_host/host1/scan

Scan target 0:

	echo "0 0 -" > /sys/class/scsi_host/host1/scan

Scan a single LUN:

	echo "0 0 0" > /sys/class/scsi_host/host1/scan

-- Patrick Mansfield


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