linux-kernel - Re: [PATCH v2 2/3] iommu/tegra-smmu: Rework .probe_device and .attach

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Message-ID: <68c13611-bc3d-5ba6-70ec-29786d69ff9a@gmail.com>
Date:   Wed, 30 Sep 2020 08:59:45 +0300
From:   Dmitry Osipenko <digetx@...il.com>
To:     Nicolin Chen <nicoleotsuka@...il.com>
Cc:     thierry.reding@...il.com, joro@...tes.org, krzk@...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 v2 2/3] iommu/tegra-smmu: Rework .probe_device and
 .attach_dev

30.09.2020 08:41, Nicolin Chen пишет:
> On Wed, Sep 30, 2020 at 08:39:54AM +0300, Dmitry Osipenko wrote:
>> 30.09.2020 03:30, Nicolin Chen пишет:
>>>  static int tegra_smmu_attach_dev(struct iommu_domain *domain,
>>>  				 struct device *dev)
>>>  {
>>> +	struct iommu_fwspec *fwspec = dev_iommu_fwspec_get(dev);
>>>  	struct tegra_smmu *smmu = dev_iommu_priv_get(dev);
>>>  	struct tegra_smmu_as *as = to_smmu_as(domain);
>>> -	struct device_node *np = dev->of_node;
>>> -	struct of_phandle_args args;
>>>  	unsigned int index = 0;
>>>  	int err = 0;
>>>  
>>> -	while (!of_parse_phandle_with_args(np, "iommus", "#iommu-cells", index,
>>> -					   &args)) {
>>> -		unsigned int swgroup = args.args[0];
>>> -
>>> -		if (args.np != smmu->dev->of_node) {
>>> -			of_node_put(args.np);
>>> -			continue;
>>> -		}
>>> -
>>> -		of_node_put(args.np);
>>> +	if (!fwspec || fwspec->ops != &tegra_smmu_ops)
>>> +		return -ENOENT;
>>
>> s/&tegra_smmu_ops/smmu->iommu.ops/
>>
>> Secondly, is it even possible that fwspec could be NULL here or that
>> fwspec->ops != smmu->ops?
> 
> I am following what's in the arm-smmu driver, as I think it'd be
> a common practice to do such a check in such a way.
> 

Please check whether it's really needed. It looks like it was needed
sometime ago, but that's not true anymore.