Re: [PATCH] iommu/iova: Fix module config properly

[Robin Murphy]

On 2022-09-13 14:01, John Garry wrote:
> On 13/09/2022 12:47, Robin Murphy wrote:
> > IOMMU_IOVA is intended to be an optional library for users to select as
> > and when they desire. Since it can be a module now, this means that
> > built-in code which has chosen not to select it should not fail to link
> > if it happens to have selected as a module by someone else. Replace
> > IS_ENABLED() with IS_REACHABLE() to do the right thing.
>
> Hi Robin,
>
> Recently you mentioned "I wonder if we couldn't replace the IS_ENABLED() 
> with IS_REACHABLE() and restore some of the previously-conditional 
> selects", and pointed me to 84db889e6d82 as an example of when a 
> conditional select was made unconditional.
>
> So will you also restore some previously-conditional selects next?

I figured I'd leave that up to Thierry (and/or anyone else with a vested 
interest), but having mulled it over since that previous thread, there's 
really no excuse for the API itself not to do the right thing either 
way, so I felt compelled to write up this much.

Cheers,
Robin.

> To me, it seems that any user of IOVA API selects IOMMU_IOVA always.
>
> thanks,
> John
>
> > CC: Thierry Reding <thierry.reding@xxxxxxxxx>
> > Reported-by: John Garry <john.garry@xxxxxxxxxx>
> > Fixes: 15bbdec3931e ("iommu: Make the iova library a module")
> > Signed-off-by: Robin Murphy <robin.murphy@xxxxxxx>
> > ---
> >
> > Phrased as a fix for the sake of complete honesty, but it seems
> > everyone's been making do for years already so by now it's really
> > just more of an enhancement.
> >
> >   include/linux/iova.h | 2 +-
> >   1 file changed, 1 insertion(+), 1 deletion(-)
> >
> > diff --git a/include/linux/iova.h b/include/linux/iova.h
> > index 8f97a43be834..fe18c3e6a725 100644
> > --- a/include/linux/iova.h
> > +++ b/include/linux/iova.h
> > @@ -75,7 +75,7 @@ static inline unsigned long iova_pfn(struct 
> > iova_domain *iovad, dma_addr_t iova)
> >       return iova >> iova_shift(iovad);
> >   }
> > -#if IS_ENABLED(CONFIG_IOMMU_IOVA)
> > +#if IS_REACHABLE(CONFIG_IOMMU_IOVA)
> >   int iova_cache_get(void);
> >   void iova_cache_put(void);