On Wednesday 27 April 2016 16:50:19 Catalin Marinas wrote: > On Wed, Apr 27, 2016 at 04:11:17PM +0200, Arnd Bergmann wrote: > > On Wednesday 27 April 2016 14:59:00 Catalin Marinas wrote: > > > > > > I would be in favour of a dma_inherit() function as well. We could hack > > > something up in the arch code (like below) but I would rather prefer an > > > explicit dma_inherit() call by drivers creating such devices. > > > > > > diff --git a/arch/arm64/include/asm/dma-mapping.h > > > b/arch/arm64/include/asm/dma-mapping.h > > > index ba437f090a74..ea6fb9b0e8fa 100644 > > > --- a/arch/arm64/include/asm/dma-mapping.h > > > +++ b/arch/arm64/include/asm/dma-mapping.h > > > @@ -29,8 +29,11 @@ extern struct dma_map_ops dummy_dma_ops; > > > > > > static inline struct dma_map_ops *__generic_dma_ops(struct device *dev) > > > { > > > - if (dev && dev->archdata.dma_ops) > > > - return dev->archdata.dma_ops; > > > + while (dev) { > > > + if (dev->archdata.dma_ops) > > > + return dev->archdata.dma_ops; > > > + dev = dev->parent; > > > + } > > > > I think this would be a very bad idea: we don't want to have random > > devices be able to perform DMA just because their parent devices > > have been set up that way. > > I agree, it's a big hack. It would be nice to have a simpler way to do > this in driver code rather than explicitly calling > of_dma_configure/arch_setup_dma_ops as per the original patch in this > thread. >
I haven't followed the entire discussion, but what's wrong with passing around a pointer to a 'struct device *hwdev' that represents the physical device that does the DMA? Arnd -- To unsubscribe from this list: send the line "unsubscribe linux-usb" in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html