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

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Message-ID: <13746922-0253-cda7-e9ac-2bd20bf1a17f@gmail.com>
Date:   Thu, 1 Oct 2020 00:24:25 +0300
From:   Dmitry Osipenko <digetx@...il.com>
To:     Nicolin Chen <nicoleotsuka@...il.com>,
        Thierry Reding <thierry.reding@...il.com>
Cc:     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

...
>> 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.