Re: [PATCH v3 2/3] iommu/tegra-smmu: Rework .probe_device and .attach_dev

[Dmitry Osipenko]

...
>  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;

In previous reply you said that these fwspec checks are borrowed from
the arm-smmu driver, but I'm now looking at what other drivers do and I
don't see them having this check.

Hence I'm objecting the need to have this check here. You either should
give a rational to having the check or it should be removed.

Please never blindly copy foreign code, you should always double-check it.