[PATCH fpga 8/9] fpga socfpga: Use the scatterlist interface

[jgunthorpe@obsidianresearch.com (Jason Gunthorpe)]

On Sun, Nov 13, 2016 at 05:19:34PM -0600, atull wrote:

> Currently or soon we have 3 drivers that don't really use the sg
> interface natively.  So this workaround ends up in each of them?

Thinking of the SG list as a workaround is not really right - the SG
list is a way to pass memory stored in non-contiguous pages around,
and the miter is a way to access them from the CPU.

socfpga *does* use sg natively because it is happy to process the data
from the CPU page-at-time. It just doesn't use DMA.

> That's a lot of duplicated code.  Why can't this code be in the
> fpga-mgr.c core for drivers that aren't using sg (to minimizing
> duplication).

Sure, if it is a common pattern it is a good idea to lift it.

I'd add a newop 'write_fragment' and a driver must define write_sg
write_fragment, if write_fragment is used then the core supplies
that loop.

Is there a tree with these new drivers someplace?

> I will test this when I get time, may not be this week.  I just
> moved to a new building and lab and am in a course all week and
> so forth.

Sure, I don't expect any problems, Zynq uses the same loop and it
seems fine.

Jason