Re: USB device allocation

danielt@digi.com
Wed, 6 Oct 1999 09:44:32 -0500 (CDT)


On Wed, 6 Oct 1999, Marcin Dalecki wrote:

> David Weinehall wrote:
> >
> > On Tue, 5 Oct 1999, Martin Dalecki wrote:
> >
> > > David Weinehall wrote:
> > > >
> > > > On Tue, 5 Oct 1999, H. Peter Anvin wrote:
> > > >
> > > > > Dan Hollis wrote:
> > > > > >
> > > > > > On Tue, 5 Oct 1999, Steffen Grunewald wrote:
> > > > > > > That's 32 entries for 16 devices...
> > > > > > > > 64 = /dev/usbscanner0 USB HP scanner
> > > > > > > > ...
> > > > > > > > 95 = /dev/usbscanner15
> > > > > > > Same here...
> > > > > > > > 128 = /dev/ttyACM0 USB modem
> > > > > > > > ...
> > > > > > > > 255 = /dev/ttyACM127
> > > > > > > What about some spare entries for USB monitors, speakers, CDrecorders ?
> > > > > >
> > > > > > The desperate need for devfs becomes all more clear.
> > > > > >
> > > > >
> > > > > Actually, the need is for a decent-sized dev_t.
> > > >
> > > > With a decently sized dev_t we will still have the problem with a
> > > > cluttered /dev directory. With devfs we won't. And if you still want your
> > > > standard, cluttered, /dev directory, you can still have it with devfs. So
> > > > I can't really understand you being so negative in regard to devfs.
> > >
> > > Inventing a dynamic fs is cluttering the way I see what a fs should be
> > > by far more then just having some superflous entries in /dev/
> >
> > Is procfs any better in this respect?!
>
> No it isn't.
>
> > Oh, and have you actually ever tried a system running devfs (such as a
> > kernel patched with Richard Gooch' patch, or a Solaris-system), or?
>
> Yes.
>
> > Hmmm. If USB isn't enough to convince, think about USB2 (128 devices/bus
> > if I'm not all wrong), FireWire, FibreChannel, SCSI-III, etc. Sooner or
> > later we need a solution to the problem with devices. And devfs is a very
> > good, thought-through, proven to work (been used in Solaris for many
> > years) and backward-compatible solution. And it's available now.
>
> You should learn to solve the problems which really arise instead of
> doing academic exercises.
>
OK, I'll bite. Gimme 1024 serial ports. Yesterday.
That is 2048 devices (standard).
Easy with devfs, pretty convoluted with dynamic major numbers.

Now: remember what the permissions were _supposed_ to be on all
of them after you did your "boot -r" Solaris style and lost them all.

Real world.

-- 
Daniel Taylor      Senior Test Engineer     Digi International
danielt@digi.com                             Open systems win.

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