linux-kernel - Re: [PATCH v8 6/6] iommu/tegra-smmu: Add pagetable mappings to debugfs

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Message-ID: <97a32c9a-2ec7-6579-7d8d-026d6f820a3e@gmail.com>
Date:   Thu, 9 Dec 2021 22:40:42 +0300
From:   Dmitry Osipenko <digetx@...il.com>
To:     Nicolin Chen <nicolinc@...dia.com>
Cc:     thierry.reding@...il.com, joro@...tes.org, will@...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 v8 6/6] iommu/tegra-smmu: Add pagetable mappings to
 debugfs

09.12.2021 22:32, Nicolin Chen пишет:
> On Thu, Dec 09, 2021 at 05:47:18PM +0300, Dmitry Osipenko wrote:
>> External email: Use caution opening links or attachments
>>
>>
>> 09.12.2021 10:38, Nicolin Chen пишет:
>>> @@ -545,6 +719,15 @@ static void tegra_smmu_detach_as(struct tegra_smmu *smmu,
>>>               if (group->swgrp != swgrp)
>>>                       continue;
>>>               group->as = NULL;
>>> +
>>> +             if (smmu->debugfs_mappings) {
>> Do we really need this check?
>>
>> Looks like all debugfs_create_dir() usages in this driver are incorrect,
>> that function never returns NULL. Please fix this.
> debugfs_create_dir returns ERR_PTR on failure. So here should be
> to check !IS_ERR. Thanks for pointing it out!
> 

All debugfs functions handle IS_ERR(). GregKH removes all such checks
all over the kernel. So the check shouldn't be needed at all, please
remove it if it's unneeded or prove that it's needed.