Re: Address spaces on a i386 - Getting Confused (fwd)

Alan Cox (alan@lxorguk.ukuu.org.uk)
Thu, 1 Apr 1999 13:38:49 +0100 (BST)


> it shows how to easily detect the weirdly-mapped cases. For user-space
> DMA to/from block devices as you're doing, I guess it is not too bad if
> DMA simply falls back to the current indirect DMA in these cases.

That is probably a very good idea. If you want to get into direct DMA you
have to get into Trition chipset bug programming and other stuff. The bttv
TV card people have a long experience of what happens when you have cards
DMAing to each other. It varies between "works fine" and "nothing happens"
via "crashes occasionally" and "I had to poweroff my ATX board to get it
back".

It isnt something to get into on the first revision.

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