Re: Adding PCMCIA support to the kernel tree -- developers needed.

[David Brownell <david-b@pacbell.net>]

> From: "Andrew Morton" <morton@nortelnetworks.com>
> 
> Device naming worries me.

Usually a smart thing to do when designing anything, even
if you're not in marketing!  :-)


> Suppose we were able to make an entire "hotplug" transaction
> synchronous and correctly serialised.  So when I "insert" my
> 3c501, the driver load and the open all happen safely and
> serially.
> 
> Well, I still want to provide a consistent and predictable
> ordering of this wrt the "hotplug" of my Acenic card.
> 
> Why?  Because I don't want them to be randomly assigned
> "eth0" or "eth1" depending on which way the wind is
> blowing.

The word I use for that characteristic is a "stable" name.
As in, "Device names visible outside the kernel should
be stable, so you can label devices and use those names
in shell scripts and sysadmin forms."

Names based on physical connectivity (PCI slot, port
on USB hub, etc) are stable almost by definition; they
change only when you connect things differently.  Some
names are more stable than that ... unique serial numbers
(like Ethernet addresses) can help.

Names like "eth0" aren't stable, nor are /proc/bus/usb
names, but /proc/bus/pci names are.  If "acenic" used
"pdev->slot_name" not "eth%d" for its interface names,
that driver would have stable naming right now.

I read recently that "stable" names were a goal of "devfs",
so I wonder if that "stable" is my "stable". 


> This means, I think, that we want *global* serialisation
> of all hotplug activity.  ....

No -- using "stable" names would solve that!  Serialization
between subsystems would be a bug in need of fixing.
Serialization within individual subsystems is likely though.

- Dave



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