Re: [PATCH 02/13] iommu: Move bus setup to IOMMU device registration

[Robin Murphy]

On 2022-04-16 01:04, Lu Baolu wrote:
> On 2022/4/14 20:42, Robin Murphy wrote:
> > @@ -1883,27 +1900,12 @@ static int iommu_bus_init(struct bus_type *bus)
> >    */
> >   int bus_set_iommu(struct bus_type *bus, const struct iommu_ops *ops)
> >   {
> > -    int err;
> > -
> > -    if (ops == NULL) {
> > -        bus->iommu_ops = NULL;
> > -        return 0;
> > -    }
> > -
> > -    if (bus->iommu_ops != NULL)
> > +    if (bus->iommu_ops && ops && bus->iommu_ops != ops)
> >           return -EBUSY;
> >       bus->iommu_ops = ops;
>
> Do we still need to keep above lines in bus_set_iommu()?

It preserves the existing behaviour until each callsite and its 
associated error handling are removed later on, which seems like as good 
a thing to do as any. Since I'm already relaxing iommu_device_register() 
to a warn-but-continue behaviour while it keeps the bus ops on 
life-support internally, I figured not changing too much at once would 
make it easier to bisect any potential issues arising from this first step.

Thanks,
Robin.