Re: Does sysfs really provides persistent hardware path to devices?

[Andrey Borzenkov <arvidjaar@mail.ru>]

On Saturday 26 July 2003 20:50, Greg KH wrote:
> On Sat, Jul 26, 2003 at 08:36:13PM +0400, Andrey Borzenkov wrote:
> > So apparently I cannot rely on sysfs to get reliable persistent
> > information about physical location of devices.
>
> That is correct, but you can get pretty close :)
>

sure, I know. The more annoying is how difficult is to step over this "close" 
:)

> > the point is - I want to create aliases that would point to specific
> > slots. I.e. when I plug USB memory stick in upper slot on front panel I'd
> > like to always create the same device alias for it.
>
> Look at the udev announcement I posted to linux-kernel yesterday to see
> how to do this.
>

I know udev.

udev does not answer my question. It operates on logical device (bus) numbers. 
My question was how to name devices based on physical position 
*independently* of logical numbers they get.

It is not strictly speaking udev fault but simply result of kernel exporting 
logical device names instead of true physical paths. I miss Solaris /devices 
filesystem ...

OK I may mot see something obvious. Simple example.

I have SCSI HBA sitting in PCI slot 3. It gets SCSI host number 1. I configure 
udev to name SCSI device 1.0.0.1 "database"

I add one more SCSI HBA in PCI slot 1. Next time system is booted *this* gets 
SCSI host number 1 and my first HBA in slot 3 gets SCSI host 2. Oops.

Question: how to configure udev so that "database" always refers to LUN 0 on 
target 0 on bus 0 on HBA in PCI slot 1.

> thanks,
>

I thank you

-andrey

PS this obviously applies not only to SCSI. It is just it is most simple 
example and you do not open network interfaces by name so there is *no* way 
at all to assign their numbers :(