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

[John Garry]

On 07/01/2021 01:18, Lu Baolu wrote:
> 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.

Hi baolu,

> 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/ 

So I did check linux-iommu lore for recent references, above, but did 
not see this one - that really should have cc'ed linux-iommu list (which 
it didn't).

> 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.

ok, fine. It also seems that this API has not had a user since it was 
introduced in v5.2.

Thanks,
John

Ps. I suppose a v3 series is not needed ATM - this patch can just be 
dropped.