Re: Device Naming under Linux [Long]
Richard Gooch (Richard.Gooch@atnf.CSIRO.AU)
Wed, 22 Apr 1998 20:26:23 +1000
Riley Williams writes:
> Hi there.
>
> >> But you are still limited to 8 bits for the major number. devices.txt
> >> tells me that half the available numbers are "in use" (either
> >> officially allocated or reserved for local/experimental use). How long
> >> before we hit the 8 bit limit?
>
> > That's a point worth considering, but take a look at the number of major
> > device numbers used for tty's alone; Suppose we collapsed all the major
> > numbers for different tty open blocking policies into one major number,
> > and expressed all these policies in part of a 24 bit minor number? Are
> > there any other devices with more than their fair share of major
> > numbers?
>
> The IDE device drivers? Memory says there's four different major numbers
> allocated to them...
There's 6 now. But I don't really see them as being particulary
wasteful. I do wonder what minors 128 to 255 are used for? Perhaps for
future expansion? (I understand there is the possibility for multiple
LUNs in future versions of the IDE spec). If you look at the IDE
naming scheme in devfs, you'll see that there is the potential for
further subdivision, so we've taken account of that.
At best we could reduce the number of IDE majors to 3, and remove that
possible future expansion room. That doesn't seem like a significant
improvement: it's just a piddling 3 majors.
Regards,
Richard....
-
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@vger.rutgers.edu