On 2020-09-15 11:09 a.m., Christoph Hellwig wrote:
On Tue, Sep 15, 2020 at 10:40:39AM -0400, Thomas Tai wrote:
+++ b/include/linux/dma-direct.h
@@ -62,9 +62,6 @@ static inline bool dma_capable(struct device *dev, dma_addr_t 
addr, size_t size,
        dma_addr_t end = addr + size - 1;
   -    if (!dev->dma_mask)
-               return false;

I am concerned that some drivers may rely on this NULL checking. Would you
think we can keep this checking and use the following WARN_ON_ONCE()?

dma_capable is not a helper for drivers, but just for dma-direct
and related code.  And this patch adds the checks for the three
places how we call into the ->map* methods.

Ok. That sounds good to me. I will make the suggested changes and run some tests before sending out the V2 patch.

Thank you,
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