Re: How to DMA data from a pci device to a user buffer directly

[Pete Zaitcev <zaitcev@redhat.com>]

> 5) My DMA controller has unlimited scatter-gather capability.

> By the way, I have tested the rest of my code by DMA the image data to a
> kernel buffer allocated using kmalloc() first, then do a memcpy() to copy
> the image data to a user buffer. This alternative seems to work fine.

Use mmap to make the kmalloc-ed buffer available to user
application without the overhead of memcpy().

It is very wonderful that you can do s/g, so on the next stage
you can kmalloc a bunch of blocks with small order (1) and use
those instead of relying on bootmem allocation and Pauline's
bigphysarea patch. Most older controllers cannot do it.

-- Pete