On Tue, Jul 12, 2011 at 3:33 PM, Linus Walleij [off-list ref] wrote:

On Tue, Jul 12, 2011 at 6:17 AM, Jassi Brar [off-list ref] wrote:

quoted

1) Striding, in one form or other, is supported by other DMACs as well.
? The number will only increase in future.
? Are we to add ?<VENDOR>_DMA_STRIDE_CONFIG for each case ?

If we are sure about this and striding will work in a similar way on all
then let's have the enum named DMA_STRIDE_CONFIG and move the
passed-in struct to <linux/dmaengine.h) then?

Would that be:

struct dma_stride_config {
? ?u32 read_bytes;
? ?u32 skip_bytes;
};

Or something more complex?

Well, I am not sure if striding needs any special treatment at all.
Why not have client drivers prepare and submit sg-list.
Let the DMAC drivers interpret/parse the sg-list and program it
as strides if the h/w supports it.
If anything, we should make preparation and submission of sg-list
as efficient as possible.

quoted

2) As Dan noted, client drivers are going to have ifdef hackery in
order to be common
?to other SoCs.

Don't think so, why? This is a runtime config entirely, and I just illustrated
in mail to Dan how that can be handled by falling back to a sglist I believe?

Runtime decision isn't neat either.
What if a client driver is common to 'N' SoCs each with different DMACs ?
We would need a switch construct !