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From: Darren Reed <avalon@coombs.anu.edu.au>
Subject: Re: converting drivers to dynamic memory...
To: gurney_j@resnet.uoregon.edu
Date: Fri, 19 Dec 1997 01:31:43 +1100 (EDT)
Cc: freebsd-hackers@FreeBSD.ORG
In-Reply-To: <19971218053840.15389@hydrogen.nike.efn.org> from "John-Mark Gurney" at Dec 18, 97 05:38:40 am
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In some mail from John-Mark Gurney, sie said:
> 
> > Hmmm.  So how exactly does the B-tree solve the problem ?  You're
> > allocating
> > the dynamic data and storing it on the B-Tree and then have to look
> > it up by
> > searching the B-tree ?  Aren't there better ways of allocating data
> > and then
> > looking up where it is (what about asking the driver itself) ?
> 
> correct.. this is EXACTLY what the code does.. the problem is that
> right now the data is stored in a static table,  because of this, you
> can't just say, hey, I need another instance of you to attach to this
> card...   we could even go with a small array of pointers that gets
> realloced/resized each time a driver gets attached...  (which might be
> better, I happen to have just finished testing the btree code, so that
> influenced my choice.. :) )..

Now I've got more clues so I can understand where you're going with all
of this :)

Well, FWIW, Solaris2 does the "extra pointer" thing in its DDI :)

However, if you are using multiple instances, you do need to keep track
of which is which (guess you could use B-Trees for this :) yourself.

Their function call interface consists of over 120 functions which support
using the extra pointer (they call their void * type dev_info_t).

Hmmm, on second thoughts maybe instead of option 1 and option 2, option 2
should be phase 1 and option 1 should be phase 2 ? :-)

Darren