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Date:   Mon, 5 Oct 2020 11:53:51 +0200
From:   Thierry Reding <thierry.reding@gmail.com>
To:     Dmitry Osipenko <digetx@gmail.com>
Cc:     Nicolin Chen <nicoleotsuka@gmail.com>, joro@8bytes.org,
        vdumpa@nvidia.com, jonathanh@nvidia.com,
        linux-tegra@vger.kernel.org, iommu@lists.linux-foundation.org,
        linux-kernel@vger.kernel.org
Subject: Re: [PATCH v4 2/3] iommu/tegra-smmu: Rework tegra_smmu_probe_device()
Message-ID: <20201005095351.GI425362@ulmo>
References: <20201002060807.32138-1-nicoleotsuka@gmail.com>
 <20201002060807.32138-3-nicoleotsuka@gmail.com>
 <b1a195cf-0127-0531-f6d1-835367511f57@gmail.com>
 <0c66bab9-0132-d3fb-ea4e-de1278cf2b04@gmail.com>
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On Fri, Oct 02, 2020 at 05:50:08PM +0300, Dmitry Osipenko wrote:
> 02.10.2020 17:22, Dmitry Osipenko =D0=BF=D0=B8=D1=88=D0=B5=D1=82:
> >>  static int tegra_smmu_of_xlate(struct device *dev,
> >>  			       struct of_phandle_args *args)
> >>  {
> >> +	struct platform_device *iommu_pdev =3D of_find_device_by_node(args->=
np);
> >> +	struct tegra_mc *mc =3D platform_get_drvdata(iommu_pdev);
> >>  	u32 id =3D args->args[0];
> >> =20
> >> +	of_node_put(args->np);
> >> +
> >> +	if (!mc || !mc->smmu)
> >> +		return -EPROBE_DEFER;
> > platform_get_drvdata(NULL) will crash.
> >=20
>=20
> Actually, platform_get_drvdata(NULL) can't happen. I overlooked this.

How so? It's technically possible for the iommus property to reference a
device tree node for which no platform device will ever be created, in
which case of_find_device_by_node() will return NULL. That's very
unlikely and perhaps worth just crashing on to make sure it gets fixed
immediately.

Thierry

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