Re: udev and devfs - The final word

[Tyler Hall]

Since we're moving toward treating device numbers as unique handles for 
devices in a system, why can't we just dynamically allocate them like 
process ID's? As each device driver loads and registers with the kernel, 
it can request a device number and the kernel can assign the next 
available one.

Tyler

Rob wrote:

> On Wednesday 31 December 2003 07:31 pm, Rob Love wrote:
>
> <snip>
>  
>
> > This is definitely an interesting problem space.
> >
> > I agree wrt just inventing consecutive numbers.  If there was a nice way
> > to trivially generate a random and unique number from some
> > device-inherent information, that would be nice.
> >
> > 	Rob Love
> >    
>
> my first thought was hardware serial numbers, but i'm guessing they mostly 
> don't exist based on the discomfort caused by the pentium 3 serial number in 
> the past. my second thought was raw latency. in the real world, 2 identical 
> devices of any nature are going to respond electrically at different rates. i 
> kind of stole the concept from what i read about the i810 rng... quantum 
> differences can distinguish between 2 of anything, and based on the response 
> time, 'cookies' can be written out to keep them separately ID'd. some devices 
> will get slower over time, e.g. increasing error rates and aging silicon will 
> throw the 'cookie' off, so you'd re-calibrate every so often, like on a 
> reboot. those are rare for some of us ;)
>
> the big IF: can you measure that with enough precision to at least decrease 
> the probablity of collision? 
>
>  

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