Re: [PATCH 02/19] dma-iommu: cleanup dma-iommu.h

[Robin Murphy]

On 01/02/2019 16:13, Christoph Hellwig wrote:
> On Fri, Feb 01, 2019 at 02:47:17PM +0000, Robin Murphy wrote:
> > On 14/01/2019 09:41, Christoph Hellwig wrote:
> > > No need for a __KERNEL__ guard outside uapi, make sure we pull in the
> > > includes unconditionally so users can rely on it, and add a missing
> > > comment describing the #else cpp statement.  Last but not least include
> > > <linux/errno.h> instead of the asm version, which is frowned upon.
> >
> > I think the __KERNEL__ and asm/errno.h slip-ups are things I cargo-culted
> > from the arch code as a fresh-faced noob yet to learn the finer details, so
> > ack for those parts. The forward-declarations, though, were a deliberate
> > effort to minimise header dependencies and compilation bloat for includers
> > who absolutely wouldn't care, and specifically to try to avoid setting
> > transitive include expectations since they always seem to end up breaking
> > someone's config somewhere down the line. Admittedly this little backwater
> > is hardly comparable to the likes of the sched.h business, but I'm still
> > somewhat on the fence about that change :/
>
> As far as I can tell almost all users of linux/dma-iommu.h require
> CONFIG_DMA_IOMMU to be enabled anyway..

Other than dma-iommu.c itself, none of them *require* it - only 
arch/arm64 selects it (the one from MTK_IOMMU is just bogus), and a lot 
of the drivers also build for at least one other architecture (and/or 
arm64 with !IOMMU_API).

Either way, I have no vehement objection to the change, I just don't see 
any positive value in it.

Robin.