linux-kernel - Re: [PATCH v3 2/3] iommu/tegra-smmu: Rework .probe_device and .attach

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Date:   Wed, 30 Sep 2020 14:32:44 -0700
From:   Nicolin Chen <nicoleotsuka@...il.com>
To:     Dmitry Osipenko <digetx@...il.com>
Cc:     Thierry Reding <thierry.reding@...il.com>, joro@...tes.org,
        krzk@...nel.org, vdumpa@...dia.com, jonathanh@...dia.com,
        linux-tegra@...r.kernel.org, iommu@...ts.linux-foundation.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH v3 2/3] iommu/tegra-smmu: Rework .probe_device and
 .attach_dev

On Thu, Oct 01, 2020 at 12:24:25AM +0300, Dmitry Osipenko wrote:
> ...
> >> It looks to me like the only reason why you need this new global API is
> >> because PCI devices may not have a device tree node with a phandle to
> >> the IOMMU. However, SMMU support for PCI will only be enabled if the
> >> root complex has an iommus property, right? In that case, can't we
> >> simply do something like this:
> >>
> >> 	if (dev_is_pci(dev))
> >> 		np = find_host_bridge(dev)->of_node;
> >> 	else
> >> 		np = dev->of_node;
> >>
> >> ? I'm not sure exactly what find_host_bridge() is called, but I'm pretty
> >> sure that exists.
> >>
> >> Once we have that we can still iterate over the iommus property and do
> >> not need to rely on this global variable.
> > 
> > I agree that it'd work. But I was hoping to simplify the code
> > here if it's possible. Looks like we have an argument on this
> > so I will choose to go with your suggestion above for now.
> 
> This patch removed more lines than were added. If this will be opposite
> for the Thierry's suggestion, then it's probably not a great suggestion.

Sorry, I don't quite understand this comments. Would you please
elaborate what's this "it" being "not a great suggestion"?