linux-kernel - Re: [PATCH v6 2/6] iommu/tegra-smmu: Rename struct tegra_smmu_group_soc *soc to *group

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Message-ID: <YV8lbCePQet+vICa@orome.fritz.box>
Date:   Thu, 7 Oct 2021 18:50:52 +0200
From:   Thierry Reding <thierry.reding@...il.com>
To:     Nicolin Chen <nicoleotsuka@...il.com>
Cc:     joro@...tes.org, will@...nel.org, vdumpa@...dia.com,
        jonathanh@...dia.com, linux-tegra@...r.kernel.org,
        iommu@...ts.linux-foundation.org, linux-kernel@...r.kernel.org,
        digetx@...il.com
Subject: Re: [PATCH v6 2/6] iommu/tegra-smmu: Rename struct
 tegra_smmu_group_soc *soc to *group_soc

On Mon, Sep 13, 2021 at 06:38:54PM -0700, Nicolin Chen wrote:
> There are both tegra_smmu_soc and tegra_smmu_group_soc using "soc"
> for their pointer instances. This patch renames the one of struct
> tegra_smmu_group_soc from "soc" to "group_soc" to distinguish it.
> 
> Signed-off-by: Nicolin Chen <nicoleotsuka@...il.com>
> ---
>  drivers/iommu/tegra-smmu.c | 17 +++++++++--------
>  1 file changed, 9 insertions(+), 8 deletions(-)

I think the context makes it clear which one this is. The "soc" field in
struct tegra_smmu_group clearly refers to the group SoC data, whereas
the "soc" field in struct tegra_smmu refers to the SMMU SoC data.

> 
> diff --git a/drivers/iommu/tegra-smmu.c b/drivers/iommu/tegra-smmu.c
> index 6ebae635d3aa..a32ed347e25d 100644
> --- a/drivers/iommu/tegra-smmu.c
> +++ b/drivers/iommu/tegra-smmu.c
> @@ -22,7 +22,7 @@
>  struct tegra_smmu_group {
>  	struct list_head list;
>  	struct tegra_smmu *smmu;
> -	const struct tegra_smmu_group_soc *soc;
> +	const struct tegra_smmu_group_soc *group_soc;
>  	struct iommu_group *grp;
>  	unsigned int swgroup;
>  };
> @@ -870,7 +870,7 @@ static struct iommu_device *tegra_smmu_probe_device(struct device *dev)
>  static void tegra_smmu_release_device(struct device *dev) {}
>  
>  static const struct tegra_smmu_group_soc *
> -tegra_smmu_find_group(struct tegra_smmu *smmu, unsigned int swgroup)
> +tegra_smmu_find_group_soc(struct tegra_smmu *smmu, unsigned int swgroup)

This one might be okay to disambiguate, but even here I think this isn't
really necessary. It's already clear from the return value what's being
returned.

>  {
>  	unsigned int i, j;
>  
> @@ -896,19 +896,20 @@ static struct iommu_group *tegra_smmu_device_group(struct device *dev)
>  {
>  	struct iommu_fwspec *fwspec = dev_iommu_fwspec_get(dev);
>  	struct tegra_smmu *smmu = dev_iommu_priv_get(dev);
> -	const struct tegra_smmu_group_soc *soc;
> +	const struct tegra_smmu_group_soc *group_soc;
>  	unsigned int swgroup = fwspec->ids[0];
>  	struct tegra_smmu_group *group;
>  	struct iommu_group *grp;
>  
>  	/* Find group_soc associating with swgroup */
> -	soc = tegra_smmu_find_group(smmu, swgroup);
> +	group_soc = tegra_smmu_find_group_soc(smmu, swgroup);
>  
>  	mutex_lock(&smmu->lock);
>  
>  	/* Find existing iommu_group associating with swgroup or group_soc */
>  	list_for_each_entry(group, &smmu->groups, list)
> -		if ((group->swgroup == swgroup) || (soc && group->soc == soc)) {
> +		if ((group->swgroup == swgroup) ||
> +		    (group_soc && group->group_soc == group_soc)) {
>  			grp = iommu_group_ref_get(group->grp);
>  			mutex_unlock(&smmu->lock);
>  			return grp;
> @@ -921,9 +922,9 @@ static struct iommu_group *tegra_smmu_device_group(struct device *dev)
>  	}
>  
>  	INIT_LIST_HEAD(&group->list);
> +	group->group_soc = group_soc;
>  	group->swgroup = swgroup;
>  	group->smmu = smmu;
> -	group->soc = soc;

As another example, it's pretty evident that group->soc refers to the
group SoC data rather than the SMMU SoC data. The latter can be obtained
from group->smmu->soc, which again is enough context to make it clear
what this is.

So I don't think this makes things any clearer. It only makes the names
more redundant and awkward to write.

Thierry

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