On Mon, Dec 08, 2014 at 06:42:09PM +0200, Laurent Pinchart wrote:
> Hi Vinod,
>
> On Monday 08 December 2014 21:44:49 Vinod Koul wrote:
> > On Mon, Dec 08, 2014 at 03:13:16PM +0100, Maxime Ripard wrote:
> > > On Mon, Dec 08, 2014 at 06:23:52PM +0530, Vinod Koul wrote:
> > > > On Mon, Dec 08, 2014 at 10:00:41AM +0200, Laurent Pinchart wrote:
> > > > > > + This should NOT be set or expected to be set for memcpy
> > > > > > operations
> > > > >
> > > > > How about "Drivers that implement memcpy operations don't need to
> > > > > implement this call." ? It makes it clearer that drivers that support
> > > > > both slave and memcpy must implement dma_slave_config.
> > > >
> > > > That is a problem we want to fix of not having drivers which implement
> > > > both slave and memcpy rely on dma_slave_config for memcpy operations.
> > > > Maxime got bitten by that recently so lets fix documentation for this
> > >
> > > I really think that while the documentation should make it clear, we
> > > should be able to support dmaengine drivers that implement both slave
> > > and async operations.
> > >
> > > It is totally allowed by the framework for now, and some hardware
> > > doesn't make any distinction between what's considered a slave
> > > transfer and a memcpy for example. So I'm not really convinced we
> > > should make that distinction in the framework either.
> >
> > the dma_slave_config simply doesn't make sense for memcpy. User should be
> > able to invoke memcpy operation without making any other configuration.
>
> Of course. My point was that your proposed patch appears (to me) to mean that
> a driver that supports memcpy must no implement dma_slave_config. What the
> documentation ought to make clear is that memcpy must work without
> dma_slave_config, but drivers that support both memcpy and slave operations
> must implement dma_slave_config for the slave operations.
Very aptly said. Here is the updated text, that I am planning to add:
- This call is mandatory for slave operations only. This should NOT be
set or expected to be set for memcpy operations.
If a driver support both, it should use this call for slave
operations only and not for memcpy ones
Let me know if we have any more holes in this :)
--
~Vinod
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