linux-kernel - Re: [PATCH v4 1/2] iommu/tegra-smmu: Unwrap tegra_smmu_group

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Message-ID: <35d789ae-7deb-7f8c-0556-98fe73f5999f@gmail.com>
Date:   Tue, 29 Sep 2020 20:41:49 +0300
From:   Dmitry Osipenko <digetx@...il.com>
To:     Nicolin Chen <nicoleotsuka@...il.com>, thierry.reding@...il.com,
        joro@...tes.org
Cc:     vdumpa@...dia.com, jonathanh@...dia.com,
        linux-tegra@...r.kernel.org, iommu@...ts.linux-foundation.org,
        linux-kernel@...r.kernel.org, hch@...radead.org
Subject: Re: [PATCH v4 1/2] iommu/tegra-smmu: Unwrap tegra_smmu_group_get

29.09.2020 09:13, Nicolin Chen пишет:
> The tegra_smmu_group_get was added to group devices in different
> SWGROUPs and it'd return a NULL group pointer upon a mismatch at
> tegra_smmu_find_group(), so for most of clients/devices, it very
> likely would mismatch and need a fallback generic_device_group().
> 
> But now tegra_smmu_group_get handles devices in same SWGROUP too,
> which means that it would allocate a group for every new SWGROUP
> or would directly return an existing one upon matching a SWGROUP,
> i.e. any device will go through this function.
> 
> So possibility of having a NULL group pointer in device_group()
> is upon failure of either devm_kzalloc() or iommu_group_alloc().
> In either case, calling generic_device_group() no longer makes a
> sense. Especially for devm_kzalloc() failing case, it'd cause a
> problem if it fails at devm_kzalloc() yet succeeds at a fallback
> generic_device_group(), because it does not create a group->list
> for other devices to match.
> 
> This patch simply unwraps the function to clean it up.
> 
> Signed-off-by: Nicolin Chen <nicoleotsuka@...il.com>
> ---

Reviewed-by: Dmitry Osipenko <digetx@...il.com>