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List:       dmaengine
Subject:    DMA_SLAVE vs DMA_SG in mv_xor
From:       Stefan Roese <sr () denx ! de>
Date:       2016-07-27 9:28:35
Message-ID: fb7caead-d292-ab30-e15a-9ee50b8df610 () denx ! de
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Hi,

I'm currently thinking about adding SG support to the "old" Marvell
XOR engine DMA driver (mv_xor.c). My use-case is to transfer an area
between system memory (represented via a scatterlist) and memory on
a PCI device. Currently the XOR driver completely lags SG support.
Now I've started comparing the APIs of both DMA_SG and DMA_SLAVE to
see, which one is better matching my use-case. And because my
device address space is contiguous, the DMA_SLAVE API with only
one scatterlist seems to be more appropriate here. Even though its
not strictly speaking a "device" that I'm transferring data with.

So my main question is, is it appropriate to add the DMA_SLAVE
infrastructure to the mv_xor driver, even though the XOR engine
is not really designed to be used on "devices" (with fixed
addresses, FIFOs etc) but more for mem2mem xfers? Or should this
SG support better be added by using the DMA_SG design?

Thanks,
Stefan
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