Re: udev and devfs - The final word

[Rob Love <rml _at_ xxxxxxxxxx>]

On Thu, 2004-01-01 at 07:34, Rob Landley wrote:

> Fundamental problem: "Unique" depends on the other devices in the system.  You 
> can't guarantee unique by looking at one device, more or less by definition.

Of course.

> Combine that with hotplug and you have a world of pain.  Generating a number 
> from a device is just a fancy hashing function, but as soon as you have two 
> devices that generate the same number independently (when in separate 
> systems) and you plug them both into the same system: boom.

A solution would have to deal with collisions.

> Of course the EASY way to deal with collisions is to just fail the hash thingy 
> in a detectable way, and punt to some kind of udev override.  So if you yank 
> a drive from system A, throw it in system B, try to re-export it NFS, and 
> it's not going to work, it TELLS you.

No no no.  Nothing this complicated.  No punting to udev.

> Solve 90% of the problem space and have a human deal with the exceptions.  How 
> big's the unique number being exported, anyway?  (If it's 32 bits, the 
> exceptions are 1 in 4 billion.  It may never be seen in the wild...)

Device numbers are 64-bit now.

	Rob Love


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