linux-kernel - Re: [PATCH v4 1/3] iommu/tegra-smmu: Use fwspec in tegra_smmu_(de)attach

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Date:   Fri, 2 Oct 2020 12:45:08 -0700
From:   Nicolin Chen <nicoleotsuka@...il.com>
To:     Dmitry Osipenko <digetx@...il.com>
Cc:     thierry.reding@...il.com, joro@...tes.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 v4 1/3] iommu/tegra-smmu: Use fwspec in
 tegra_smmu_(de)attach_dev

On Fri, Oct 02, 2020 at 05:41:50PM +0300, Dmitry Osipenko wrote:
> 02.10.2020 09:08, 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)
> > +		return -ENOENT;
> 
> Could the !fwspec ever be true here as well?

There are multiple callers of this function. It's really not that
straightforward to track every one of them. So I'd rather have it
here as other iommu drivers do. We are human beings, so we could
have missed something somewhere, especially callers are not from
tegra-* drivers.