On Tuesday 07 January 2014, Yao Yuan wrote:

Thanks for your suggestion. It's important for me.

I read the source code for dma_map_single again. I found that both of them(as first argument is
dma or uart) worked well. But in my code I found that the *sport->port.dev->dma_mask is not
zero. By contrast the dma_mask for dma device is zero.

Ah, it seems you found two more bugs then ;-)

You are right. There should be dma device. But I also have a doubt here. Why I find many other
driver use the first argument here rather than the dma device pointer.

It's a common mistake. Most other linux device driver interfaces require you to pass the
device you are working on, so it's understandable why people come to the wrong conclusion
here.

	Arnd