Re: Minor numbers

[Andries.Brouwer@cwi.nl]

> Im very interested in 32bit dev_t or at least implementing
> the 'lots of majors' half of it because we are probably
> going to need it in the 2.5 years before we have a 2.6

Yes, a larger dev_t has been desirable for a long time,
and more and more kludges are invented to work around its lack.
Still, changing this is fairly simple.

I firmly believe that we want to go to 64-bit. In case there
is an intermediate step, that means that it would have to be 16+16,
in order not to introduce complications later.

>> The system call itself cannot easily be changed to take a larger dev_t,
>> mostly because under old glibc the high order part would be random.

> Is that true or is it always happening to be clear ?

I wrote that talking about 64-bit dev_t. For 32-bit one might be
slightly more optimistic. The C calling conventions will widen a
short to an int, I suppose.
It is true however that older glibc does its best to make sure
the kernel doesnt see more than 16 bits:

  int
  __xmknod (int vers, const char *path, mode_t mode, dev_t *dev) {
	unsigned short int k_dev;
	k_dev = ((major (*dev) & 0xff) << 8) | (minor (*dev) & 0xff);
	return __syscall_mknod (path, mode, k_dev);
  }

Andries