Re: [PATCH v4 1/2] PCI: Take other bus devices into account when distributing resources

[Mika Westerberg <mika.westerberg@linux.intel.com>]

Hi,

On Thu, Jan 05, 2023 at 11:04:13AM -0600, Bjorn Helgaas wrote:
> On Thu, Jan 05, 2023 at 03:43:29PM +0200, Mika Westerberg wrote:
> > On Thu, Jan 05, 2023 at 11:12:11AM +0200, Mika Westerberg wrote:
> > > > What happens in a topology like this:
> > > > 
> > > >   10:00.0 non-hotplug bridge to [bus 20-3f]
> > > >   10:01.0 non-hotplug bridge to [bus 40]
> > > >   20:00.0 hotplug bridge
> > > >   40:00.0 NIC
> > > > 
> > > > where we're distributing space on "bus" 10, hotplug_bridges == 0 and
> > > > normal_bridges == 2?  Do we give half the extra space to bus 20 and
> > > > the other half to bus 40, even though we could tell up front that bus
> > > > 20 is the only place that can actually use any extra space?
> > > 
> > > Yes we split it into half.
> > 
> > Forgot to reply also that would it make sense here to look at below the
> > non-hotplug bridges and if we find hotplug bridges, distribute the space
> > equally between those or something like that?
> 
> Yes, I do think ultimately it would make sense to keep track at every
> bridge whether it or any descendant is a hotplug bridge so we could
> distribute extra space only to bridges that could potentially use it.
> 
> But I don't know if that needs to be done in this series.  This code
> is so complicated and fragile that I think being ruthless about
> defining the minimal problem we're solving and avoiding scope creep
> will improve our chances of success.
> 
> So treat this as a question to improve my understanding more than
> anything.

Okay, undestood ;-)