Example PPC-4xx DMA scatter/gather usage

[Buhler, Greg]

Does anyone have any example code they could provide me that shows
correct usage of the Linux 2.6.x PPC-4xx scatter/gather DMA
functionality? None of the mainline kernel tree sources or module
sources seem to use this functionality. 

I am working on a driver that runs on an embedded PPC-405gp running
linux 2.4.21.  The driver relies extensively on the PPC's DMA controller
using all 4 channels simultaneously.  After some research I determined
that the version of the dma code that was in 2.4.21 had been
significantly modified in more recent kernel trees. As a result I have
merged in the 2.6.x version of this code, but am running into some
trouble with sg transfers.  Specifically, after setting up an sgl the
way I used to with the 2.4.21 kernel, and then kicking off the transfer,
nothing seems to get transferred. When I attempt to remove sg elements
from the sgl, the kernel complains saying that I'm trying to remove an
element from an already empty sgl.

Any help, advice, or examples would be greatly appreciated. Thanks.
______________________
Greg Buhler
Embedded INFOSEC Systems
Network Systems Group
ViaSat, Inc
760.476.2699
greg.buhler at viasat.com

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