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Subject: Re: [PATCH v1] iommu/tegra-smmu: Change debugfs directory name
To:     Joerg Roedel <joro@8bytes.org>
Cc:     Thierry Reding <thierry.reding@gmail.com>,
        Jonathan Hunter <jonathanh@nvidia.com>,
        Krishna Reddy <vdumpa@nvidia.com>,
        Will Deacon <will@kernel.org>, linux-tegra@vger.kernel.org,
        iommu@lists.linux-foundation.org, linux-kernel@vger.kernel.org
References: <20210712001341.11166-1-digetx@gmail.com>
 <YO7B56Mkz3kx5U5Q@8bytes.org>
From:   Dmitry Osipenko <digetx@gmail.com>
Message-ID: <43abb785-8b6a-555b-7d66-fa1911d2f8a0@gmail.com>
Date:   Wed, 14 Jul 2021 14:17:48 +0300
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14.07.2021 13:52, Joerg Roedel пишет:
> On Mon, Jul 12, 2021 at 03:13:41AM +0300, Dmitry Osipenko wrote:
>> -	err = iommu_device_sysfs_add(&smmu->iommu, dev, NULL, dev_name(dev));
>> +	err = iommu_device_sysfs_add(&smmu->iommu, dev, NULL, "smmu");
> 
> Are you sure no one is relying on the old name so that this change
> breaks ABI?

IIUC, Thierry and Jon have a testing suite that uses the old name, but
it shouldn't be a problem to support the new name in addition to the old
name since it's internal/private testing suite.

The reason I'm proposing this change is because it's not obvious where
the SMMU debug is located when you look at the debugfs directory, it
takes some effort to find it.

> Also this change means that there is always be only one SMMU
> per system. Is that guaranteed too?

A single SMMU is guaranteed here. Only latest Tegra SoCs have two SMMUs
and those are ARM SMMUs, while this is a legacy Tegra SMMU here.