On 03/27/2012 05:31 AM, Avi Kivity wrote:
I think the better approach is to have a PCNorthBridge base-class that
contains functionality like PAM/SRAM that both I440FX and Q35 inherit
from.
I hate to transform this into a languagey discussion, but I don't think
inheritance is the right thing here. While both 440fx and q35 are north
bridges, the similar implementation of PAM/SMRAM is not part of that.
It's just a random result of the chips' evolution. I think the code for
PAM/SMRAM can be reused if the specs match, but using a has-a instead of
an is-a relationship.
The direction I was heading with the i440fx, the i440fx has-a i440fx-pmc and it
was the pmc that actually did PAM/SMRAM.
I don't recall there being significant i440fx specific logic in the i440fx-pmc
so it's entirely possible the the i440fx-pmc could be renamed to PCNorthBridge
and then both the i440fx and q35 could has-a the same PCNorthBridge (possible
with some properties to control certain behaviors.
We really need to push forward with the refactoring to find the right model
here.
Regards,
Anthony Liguori
As a counterexample, consider a northbridge that implements PAM/SMRAM
differently. You'd have to refactor PCNorthBridge into two separate
classes. With the other approach the new northbridge simply doesn't
include the existing PAM/SMRAM implementation and instead implements its
own.
