Re: What is scatter/ gather. I am making a frame grabber with DMA.

[Drew Eckhardt <drew@PoohSticks.ORG>]

In message <008a01c1fde8$0c00bee0$4c65fea9@dan>, support@pixelsmart.com writes:
>I am making a frame grabber with DMA. I assumed I could write 256K to =
>one contiguous address. Then I leared a little bit about scatter gather. =
>What is it and how does it limit my 256K image capture ?

During normal operation, modern operating systems allocate memory on page 
(almost always 4K) boundaries.  If you want to DMA directly into this memory
(which may be mapped contiguously within a processes' address space) rather
than into a contiguous buffer allocated on startup which then gets copied
as necessary you need to be able to accomodate DMAs into discontigous
memory locations.