On Tuesday 05 May 2015 11:24:03 Tom Lendacky wrote:

On 05/05/2015 11:13 AM, Suravee Suthikulanit wrote:

quoted

On 5/5/2015 11:12 AM, Arnd Bergmann wrote:

quoted

On Tuesday 05 May 2015 11:09:38 Suravee Suthikulanit wrote:

quoted

However, codes in several places are making use of dma_map_ops without
checking if the ops are NULL (i.e.
include/asm-generic/dma-mapping-common.h and in arch-specific
implementation). If setting it to NULL is what we are planning to
support, we would need to scrub the current code to put NULL check.
Also, would you consider if that is safe to do going forward?

I mean the dma_mask pointer, not dma_map_ops.

Except a lot of drivers will actually set the dma_mask pointer during
probe (usually by setting dev->dma_mask = &dev->coherent_dma_mask or by
calling dma_coerce_mask_and_coherent).  So I think the dummy_dma_ops
might be the safest way to go.

Those drivers are broken already, I don't think we should worry about
them. Let's just fix them properly when we run into problems with them.

Basically any use of dma_coerce_mask_and_coherent() is an annotation
for a bug where a driver used to set dev->dma_mask = &dev->coherent_dma_mask
manually.

	Arnd