Re: udev and devfs - The final word

Tyler Hall
2004-01-02T03:53:09Z

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:
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><snip>
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>
>>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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