Re: PCI - address management

[Robin Farine <robin dot farine at acn-group dot ch>]

On Fri, 2003-02-21 at 19:52, Gary Thomas wrote:

> > You lost me here. I thought that any PCI device powers up "dumb" and
> > remains in this state until a host/bridge configures and enables it.
> > 
> 
> Indeed.  However, this device looks like it only has one PCI region
> when it turns on, but after initialization, it has four!  The PCI
> library scanning code will only set up the first one which is 
> insufficient for my needs.

Ah, that makes it clearer.

> Truly, this is only a guess.  The problem is that the device can only
> tell the library how big a given segment is by resizing it :-(  The code
> has always just punted on this - note the comment which says something
> like "device active, probed sizes are invalid". 

In a normal case, I guess that either the OS has already initialized and
registered the device in a table somewhere (and thus knows the BARs'
sizes) or it can safely disable it (since it doesn't use it yet) and
resize the BARs. So I suppose that in your case, this device needs a 
initialization in three steps: setup first BAR, peek/poke some values in
this first region, initialize the remaining BARs?

If this assumption is correct, wouldn't it then be possible for this
device's driver to detect that the remaining BARs need initialization
and do it after the initial PCI setup stuff? 

> 
> This really only matters if you need to enable a device which didn't
> get configured the first time around - my very special case.  In all
> other cases, this code will have no real effect.

Agreed.

-- 
rnf