On Jun 25, 2005, at 1:25 PM, Erik E. Fair wrote:

> I know that bus_dma(9) was build in part to deal with other DMA  
> broken-ness
> to do with ISA DMA controllers that couldn't address more than 16  
> bits, and
> thus kernel low-memory bounce buffers had to be allocated for them  
> and the
> bus_dma(9) code would copy bytes around as necessary. Am I remembering
> correctly?

bus_dma() was built to abstract the implementation of DMA on a  
platform, not really to deal with bugs.

We could add this sort of capability, I guess... but it would require  
all of the back-ends to implement all of the bounce buffering  
capability... and for what?  For a single broken device?

-- thorpej