[Xorg] The big multiconsole nasty

Jesse Barnes jbarnes at engr.sgi.com
Thu Jul 15 06:18:00 PDT 2004

On Thursday, July 15, 2004 5:40 am, Egbert Eich wrote:
> Alan Cox writes:
>  > On Maw, 2004-07-13 at 20:18, Jesse Barnes wrote:
>  > > Sure, that would be even better.  For legacy space, size would usually
>  > > be 64k, right?  Or would we want to add a 'base' argument and allow
>  > > callers to just map the ports they're interested in?
>  >
>  > For platforms where port space can be bigger than 16bit and when port
>  > space is mmio mapped I can see it helping.
> Are there such platforms - and is this relevant at all today?

Yes, and I think so.

> I always thought that PIO was a cheap way of implementing HW
> access in days where you only had 16 memory address lines and
> address decoders were expensive so that you only wanted to
> decode a few address lines.
> Therefore today I'd expect MMIO would be the method of choice
> if HW required more than a few ports or does not have to care
> about legacy.

Right, I think most drivers will use MMIO once they're up.  However, POSTing 
devices with x86 option ROMs means using legacy I/O ports.


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