From mboxrd@z Thu Jan  1 00:00:00 1970
From: James Bottomley <James.Bottomley@HansenPartnership.com>
Subject: Re: [patch] convert the scsi layer to use struct device
Date: Mon, 17 Mar 2008 08:55:50 -0500
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To: Kay Sievers <kay.sievers@vrfy.org>
Cc: James.Smart@Emulex.Com, Greg KH <greg@kroah.com>, linux-scsi@vger.kernel.org, Tony Jones <tonyj@suse.de>

On Mon, 2008-03-17 at 14:40 +0100, Kay Sievers wrote:
> On Mon, 2008-03-17 at 08:18 -0400, James Smart wrote:
> > Greg KH wrote:
> > > I take it you haven't even looked at how !SYSFS_DEPRECATED works today,
> > > have you?  Try it and you will see that the namespace issue has been
> > > taken care of a long time ago :)
> > 
> > You are right...   but I would assume it can be answered without pushing
> > someone back into the internals of the code to figure it out.
> 
> Oh, I already answered it in an earlier mail :)
>   "these links don't exist with !SYSFS_DEPRECATED, because the
>    class devices live in subdirectories, named after the class
>    they come from, there is no namespace problem"
> 
> This is how a LUN looks now:
>   tree /sys/devices/pci0000:00/0000:00:1d.7/usb5/5-1/5-1:1.0/host13/target13:0:0/13:0:0:0/
>   /sys/devices/pci0000:00/0000:00:1d.7/usb5/5-1/5-1:1.0/host13/target13:0:0/13:0:0:0/
>   |-- block
>   |   `-- sdb
>   |       |-- subsystem -> ../../../../../../../../../../../class/block
> 
>   |       |-- sdb1
>   |       |   |-- subsystem -> ../../../../../../../../../../../../class/block
> 
>   |       |-- sdb2
>   |       |   |-- subsystem -> ../../../../../../../../../../../../class/block
> 
>   |-- bsg
>   |   `-- 13:0:0:0
>   |       |-- subsystem -> ../../../../../../../../../../../class/bsg
> 
>   |-- scsi_disk
>   |   `-- 13:0:0:0
>   |       |-- subsystem -> ../../../../../../../../../../../class/scsi_disk
> 
>   |-- scsi_generic
>   |   `-- sg2
>   |       |-- subsystem -> ../../../../../../../../../../../class/scsi_generic
> 

So the real answer is that the backlink <class>:<class device> becomes
the directory hierarchy <class>/<class device>.

The uniqueness is hopefully solved essentially because the <class> name
has to be unique.  As long as there's no clash with the actual device
property names (not necessarily a given) we're fine.

I suppose it means we have to be a bit more careful about sysfs device
file names from now on.

James