On Fri, Jul 23, 2021 at 06:44:04PM +0100, Jonathan Cameron wrote:

Mark Brown [off-list ref] wrote:

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@Mark.  This has come up a few times recently.  Are we now safe to assume
that regmap will always copy data when used with SPI and hence we no
longer need to ensure DMA safe buffers?     

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Only for single register I/O, I'd not assume that for things like raw
I/O.

Thanks for the confirmation.  So in this driver that means we
need DMA safe buffers for the regmap_bulk_ calls.  Easiest approach
is probably to use a __cacheline_aligned buffer at the end of the
iio_priv() structure.

Yeah, it might be fine depending on the bus/format type but it's not
something you can generally assume.