Subject: Re: PCI devices under MOL
From: Samuel Rydh (samuel@waltari.theophys.kth.se)
Date: Thu Nov 29 2001 - 03:17:43 MST
>> I have an application which requires direct access to hardware in a PCI
>> slot, but under MOL the PCI bus doesn't seem to be visible.
>>
>> Is there any way of releasing the PCI bus from Linux and using it from
>> MACOS?
>
>Not as far as I know...
...
> wrt PCI I believe that
>previous discussions have suggested that it is possible, however nothing
>has come of it to my knowledge, sorry. The best answer is "sooner if you
>help write it".
What one could do, with some hacking, is adding an entry to the
virtual PCI bus MacOS sees under MOL and write a wrapper
which forwards reads and writes to the real card. There are a
few caveats though.
- The virtual PCI bus/bridge does not implement PCI I/O space
(memory mapped I/O must be used).
- Linux must not access the card simultaneously.
- Bus mastering is *quite* tricky to implement. Addresses
MacOS consider to be physical can't be passed directly to
the card (since they are not really physical addresses).
Moreover, mac-ram pages are not even physically continuous
so a simple address translation and page locking won't do the
trick either.
If the card does not use DMA, the wrapper method will work
without much trouble. I've successfully got both my
ATI Rage 128 card and the Platinum chip working this way.
In both cases without graphics acceleration (which
requires bus mastering, at least in the former case).
Cheers,
/Samuel
This archive was generated by hypermail 2a24 : Thu Nov 29 2001 - 03:31:52 MST