Re: [PATCH v2 6/6] iommu: Delete iommu_dev_has_feature()

[Lu Baolu]

On 1/6/21 9:35 PM, John Garry wrote:
> Function iommu_dev_has_feature() has never been referenced in the tree,
> and there does not appear to be anything coming soon to use it, so delete
> it.

It will be used by the device driver which want to support the aux-
domain capability, for example, below series is under discussion.

https://lore.kernel.org/linux-pci/160408357912.912050.17005584526266191420.stgit@xxxxxxxxxxxxxxxxxxxxxxxxxx/

The typical use case is

        if (iommu_dev_has_feature(dev, IOMMU_DEV_FEAT_AUX)) {
                rc = iommu_dev_enable_feature(dev, IOMMU_DEV_FEAT_AUX);
                if (rc < 0) {
                        dev_warn(dev, "Failed to enable aux-domain: 
%d\n", rc);
                        return rc;
                }
        }

So please don't remove it.

Best regards,
baolu

> Signed-off-by: John Garry <john.garry@xxxxxxxxxx>
> ---
>   drivers/iommu/iommu.c | 11 -----------
>   include/linux/iommu.h |  7 -------
>   2 files changed, 18 deletions(-)
>
> diff --git a/drivers/iommu/iommu.c b/drivers/iommu/iommu.c
> index 20201ef97b8f..91f7871f5a37 100644
> --- a/drivers/iommu/iommu.c
> +++ b/drivers/iommu/iommu.c
> @@ -2853,17 +2853,6 @@ EXPORT_SYMBOL_GPL(iommu_fwspec_add_ids);
>   /*
>    * Per device IOMMU features.
>    */
> -bool iommu_dev_has_feature(struct device *dev, enum iommu_dev_features feat)
> -{
> -	const struct iommu_ops *ops = dev->bus->iommu_ops;
> -
> -	if (ops && ops->dev_has_feat)
> -		return ops->dev_has_feat(dev, feat);
> -
> -	return false;
> -}
> -EXPORT_SYMBOL_GPL(iommu_dev_has_feature);
> -
>   int iommu_dev_enable_feature(struct device *dev, enum iommu_dev_features feat)
>   {
>   	const struct iommu_ops *ops = dev->bus->iommu_ops;
> diff --git a/include/linux/iommu.h b/include/linux/iommu.h
> index 72059fcfa108..91d94c014f47 100644
> --- a/include/linux/iommu.h
> +++ b/include/linux/iommu.h
> @@ -626,7 +626,6 @@ static inline void dev_iommu_priv_set(struct device *dev, void *priv)
>   int iommu_probe_device(struct device *dev);
>   void iommu_release_device(struct device *dev);
>   
> -bool iommu_dev_has_feature(struct device *dev, enum iommu_dev_features f);
>   int iommu_dev_enable_feature(struct device *dev, enum iommu_dev_features f);
>   int iommu_dev_disable_feature(struct device *dev, enum iommu_dev_features f);
>   bool iommu_dev_feature_enabled(struct device *dev, enum iommu_dev_features f);
> @@ -975,12 +974,6 @@ const struct iommu_ops *iommu_ops_from_fwnode(struct fwnode_handle *fwnode)
>   	return NULL;
>   }
>   
> -static inline bool
> -iommu_dev_has_feature(struct device *dev, enum iommu_dev_features feat)
> -{
> -	return false;
> -}
> -
>   static inline bool
>   iommu_dev_feature_enabled(struct device *dev, enum iommu_dev_features feat)
>   {