Lee Revell wrote:

Please use DMA_32BIT_MASK (see include/linux/dma-mapping.h) instead of
0xffffffff. 

No prob.  But did you see this comment:

/*
  * NOTE: do not use the below macros in new code and do not add new 
definitions
  * here.
  *
  * Instead, just open-code DMA_BIT_MASK(n) within your driver
  */

So I guess I should use DMA_BIT_MASK(32) instead.

I've personally fixed a heisenbug in an ALSA driver
caused by incorrectly typed DMA mask...

Can you explain to me what all of this does?  Is it okay to use a static 
u64 variable?  Why do so many drivers do it that way?  I don't even know 
if 0xFFFFFFFF is the right number for my platform.