Re: [PATCH v2 03/14] PCI/P2PDMA: Add constants for not-supported result upstream_bridge_distance()

From: Logan Gunthorpe
Date: Thu Aug 08 2019 - 11:59:20 EST

On 2019-08-08 1:31 a.m., Christoph Hellwig wrote:
> On Wed, Aug 07, 2019 at 09:58:06AM -0600, Logan Gunthorpe wrote:
>> We only calculate it at the same time as we calculate the distance. This
>> is necessary because, to calculate the type, we have to walk the tree
>> and check the ACS bits. If we separated it, we'd have to walk the tree
>> twice in a very similar way just to determine both the distance and the
>> mapping type.
> Calculating it together makes perfect sense. What I find odd is the
> overloading of a single return value. Why not return the map type as
> the return value, and the distance as a by reference argument to keep
> them properly separated?

Ok, understood. I'll make that change and send some incremental patches
to Bjorn tomorrow.