Re: [PATCH 3/3] PCI: Set pref for mem64 resource of pcie device

From: Benjamin Herrenschmidt
Date: Thu Apr 09 2015 - 05:16:36 EST

On Wed, 2015-04-08 at 21:11 -0700, Yinghai Lu wrote:
> That way should be more intrusive to current code, as we are using
> type_mask checking to share the code among
> parent(pref)/child(pref), parent(no-pref)/child(pref), and
> parent(no-pref)/child(pref)

That's fine, as long as the helper knows which one is the parent and
which one is the child.

In fact, as "cute" as the mask trick is, I think it would generally make
the code more self explanatory if it explicitly tested for the
combinations that are supported, ie something like

if (parent_is_pref && !child_is_pref && child->pcie_only)
else if (!parent_is_pref)

The impact in performance would be in the noise and the logic of the
algorithm a LOT more explicit.


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