Re: proper ioport space allocation
Brian Gerst (bgerst@quark.vpplus.com)
Thu, 17 Dec 1998 13:32:03 -0500
Bob McElrath wrote:
>
> I've been playing with the pas2 (sound) module on my Alpha (because it works
> on Intel, but not Alpha), and have discovered that this module never
> allocates any portspace. (i.e. cat /proc/ioports shows no mention of the
> PAS16 driver). Now in looking through the developer's kit and such I have
> discovered that this card uses an absolute boatload of portspace. It starts
> at 0x388 and uses harmonics (of 0x400) above that, as well as one other
> random port. (List below)
>
> Now, is this normal for a card? Do all hardware devices use higher
> harmonics like this? I've inserted code to check and allocate all the
> portspace this card uses, but I'm not sure this is correct. Here's a
> snippet of the monster: (from pas2_card.c, roundabouts line 300 in
> detect_pas_hw(...))
Some ISA cards only decode 10 address lines, so they might answer to an
i/o request at port+n*0x400. This is a common problem with some S3
video cards that conflict with COM4 serial ports. My guess is that the
pas2 is one of these cards, so the dev kit suggests allocating all the
upper aliases to avoid another card's iospace.
--
Brian Gerst
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