linux-kernel - Re: [PATCH v5 2/3] iommu/tegra-smmu: Rework tegra_smmu_probe

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Message-ID: <4a5a5b1c-080a-327a-1e2f-dc087948e1a1@gmail.com>
Date:   Sat, 3 Oct 2020 17:06:42 +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
Subject: Re: [PATCH v5 2/3] iommu/tegra-smmu: Rework tegra_smmu_probe_device()

03.10.2020 09:59, Nicolin Chen пишет:
>  static int tegra_smmu_of_xlate(struct device *dev,
>  			       struct of_phandle_args *args)
>  {
> +	struct platform_device *iommu_pdev = of_find_device_by_node(args->np);
> +	struct tegra_mc *mc = platform_get_drvdata(iommu_pdev);
>  	u32 id = args->args[0];
>  
> +	put_device(&iommu_pdev->dev);
> +
> +	if (!mc || !mc->smmu)
> +		return -EPROBE_DEFER;

I'm not very excited by seeing code in the patches that can't be
explained by the patch authors and will appreciate if you could provide
a detailed explanation about why this NULL checking is needed because I
think it is unneeded, especially given that other IOMMU drivers don't
have such check.

I'm asking this question second time now, please don't ignore review
comments next time.