Re: My $0.02 on devd and devfs
H. Peter Anvin (hpa@transmeta.com)
Sun, 10 Oct 1999 21:31:39 -0700
Johannes Erdfelt wrote:
>
> Thanks for putting forth your input into the matter.
>
> I'd like to here your thoughts on major/minor allocation for PnP
> devices. The hypothetical example being used is connecting 1000+ modems
> to a machine. (Apparentely someone has done this on an Irix machine
> further solidifying the fact this can and will happen).
>
> Right now, it's impossible to do with the current 8/8 split of
> major/minor. Some people are proposing increasing it a 16/16 split which
> will significantly improve the situation, but as we've fallen into in
> the past, any arbitrary limit will be broken.
>
> Do you think simply increasing the major/minor will solve the problem?
> It seems like when you increase the major/minor space you also increase
> computational complexity in determining which driver owns that
> major/minor.
>
Not so -- the driver is always determined by some number of
left-associated bits (like an IP route); ideally it should always be the
major number.
I am proposing a 32/32 split (with a 12/20 split for NFSv2), because
glibc already is using a 64-bit dev_t. Adding thousands of modems
therefore is not a problem, and I believe it would be very hard to
construct a scenario at which this will not be sufficient for a very
long time.
-hpa
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