Re: [PATCH] swiotlb: swiotlb_{alloc,free}_buffer should depend on CONFIG_DMA_DIRECT_OPS

[Christoph Hellwig]

On Sat, Mar 24, 2018 at 04:05:45PM -0400, Konrad Rzeszutek Wilk wrote:
> > > > Otherwise we might get unused symbol warnings for configs that built
> > > > swiotlb.c only for use by xen-swiotlb.c and that don't otherwise select
> > > > CONFIG_DMA_DIRECT_OPS, which is possible on arm.
> > > > 
> > > > Fixes: 16e73adbca76 ("dma/swiotlb: Remove swiotlb_{alloc,free}_coherent()")
> > > > Reported-by: Stephen Rothwell <sfr@xxxxxxxxxxxxxxxx>
> > > > Signed-off-by: Christoph Hellwig <hch@xxxxxx>
> > > 
> > > 
> > > Alternatively could we set the Kconfig to slect DMA_DIRECT_OPS?
> > 
> > 
> > IFF we build swiotlb.c only for xen-swiotlb we don't need DMA_DIRECT_OPS.
> 
> I don't think there is ever an case where you want a Xen specific build.

arm never uses swiotlb directly, so any swiotlb.c build on arm is purely
for xen-swiotlb.c