Re: [patch] dynamic char and block devices

Richard Gooch (rgooch@ras.ucalgary.ca)
Wed, 13 Oct 1999 22:32:00 -0600


Oliver Xymoron writes:
> On Wed, 13 Oct 1999, Richard Gooch wrote:
>
> > > Since it looks doubtful that devfs will get applied anytime soon, do
> > > you have an alternate solution to suggest?
> >
> > No. Unless you store the fops with the inode, you don't have much
> > choice but to do a table lookup. So far it hasn't hurt us because the
> > lookup is an index operation, which is fast.
>
> However open(2) is not an index operation, even on devfs.

Not sure what you're trying to say here. Devfs does this by accessing
a structure member. So there are no searches required. So it's true to
say that devfs doesn't have an index operation. That's because it
doesn't have a major array in the first place.

> Having a hash on a kdev_t behind it ain't so bad. Since we'll
> eventually need more device address space, and _mandatory_ devfs
> will almost certainly not happen, some scheme other than direct
> mapping needs to be created.

I agree. My point is just that devfs gives you the option of avoiding
this new overhead. Obviously, the current major table has to be
replaced.

Regards,

Richard....
Permanent: rgooch@atnf.csiro.au
Current: rgooch@ras.ucalgary.ca

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