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SubjectRe: [PATCH v4 8/8] iommu/vt-d: Misc macro clean up for SVM
On Mon, 02 Dec 2019 10:22:13 -0800
Joe Perches <joe@perches.com> wrote:

> On Mon, 2019-12-02 at 10:15 -0800, Jacob Pan wrote:
> > On Thu, 21 Nov 2019 13:37:10 -0800
> > Joe Perches <joe@perches.com> wrote:
> >
> > > On Thu, 2019-11-21 at 13:26 -0800, Jacob Pan wrote:
> > > > Use combined macros for_each_svm_dev() to simplify SVM device
> > > > iteration and error checking.
> > > []
> > > > diff --git a/drivers/iommu/intel-svm.c
> > > > b/drivers/iommu/intel-svm.c
> > > []
> > > > +#define for_each_svm_dev(sdev, svm, d) \
> > > > + list_for_each_entry((sdev), &(svm)->devs, list)
> > > > \
> > > > + if ((d) != (sdev)->dev) {} else
> > > > +
> > > > int intel_svm_bind_mm(struct device *dev, int *pasid, int
> > > > flags, struct svm_dev_ops *ops) {
> > > > struct intel_iommu *iommu =
> > > > intel_svm_device_to_iommu(dev); @@ -274,15 +278,13 @@ int
> > > > intel_svm_bind_mm(struct device *dev, int *pasid, int flags,
> > > > struct svm_dev_ goto out; }
> > > >
> > > > - list_for_each_entry(sdev, &svm->devs,
> > > > list) {
> > > > - if (dev == sdev->dev) {
> > > > - if (sdev->ops != ops) {
> > > > - ret = -EBUSY;
> > > > - goto out;
> > > > - }
> > > > - sdev->users++;
> > > > - goto success;
> > > > + for_each_svm_dev(sdev, svm, dev) {
> > > > + if (sdev->ops != ops) {
> > > > + ret = -EBUSY;
> > > > + goto out;
> > > > }
> > > > + sdev->users++;
> > > > + goto success;
> > > > }
> > >
> > > I think this does not read better as this is now a
> > > for_each loop that exits the loop on the first match.
> > >
> > I think one of the benefits is reduced indentation. What do you
> > recommend?
>
> Making the code intelligible for a reader.
>
> At least add a comment describing why there is only
> a single possible match.
>
> Given the for_each name, it's odd code that only the
> first match has an action.
>
I will add a comment to explain we are trying to find the matching
device on the list.

Thanks

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