[PATCH 1/5] dmaengine: dw_dmac: move to generic DMA binding

On 29 January 2013 19:01, Arnd Bergmann [off-list ref] wrote:

Ah, good. So I guess the "dma-requests" property should actually
be "16" then.

yes, even i was checking on that separately :)

Does this mean that an implicit zero request line means memory?

No. 0 is also request line for a peripheral and numbers are from 0 to 15.
memcpy are identified by setting type of transfer as memcpy.

Could we have device-to-device DMAs with this controller, and if
we can, should we have both 'src' and 'dst' fields? Are the
two number ranges sharing the same address space, i.e. is
request '7' as the destination guaranteed to be the same device
as request '7' in the source?

Request lines are per master... So, for a master single request line
is independent of direction. Many DMA controllers have capability of
doing dev-to-dev transfers but DMAENGINE doesn't have any support
for it, even we don't have a usecase too :)

If we need two lines, we could interleave them with the bus
master numbers:

not required.

In theory, we could use bit-stuffing to put them all into
a single 32 bit word I guess, but generally people don't
seem to like that for new bindings.

:)

--
viresh