On Thu, Oct 16, 2014 at 07:15:40PM +0300, Laurent Pinchart wrote:
> Hi Maxime,
>
> Thank you for the patch.
>
> On Thursday 16 October 2014 12:17:05 Maxime Ripard wrote:
> > dma_slave_caps is very important to the generic layers that might interact
> > with dmaengine, such as ASoC. Unfortunately, it has been added as yet
> > another dma_device callback, and most of the existing drivers haven't
> > implemented it, reducing its reliability.
> >
> > Introduce a generic behaviour and a flag to trigger it. In case this flag
> > hasn't been set, fall back to the old mechanism.
> >
> > Signed-off-by: Maxime Ripard <maxime.ripard@xxxxxxxxxxxxxxxxxx>
> > ---
> > include/linux/dmaengine.h | 25 +++++++++++++++++++++----
> > 1 file changed, 21 insertions(+), 4 deletions(-)
> >
> > diff --git a/include/linux/dmaengine.h b/include/linux/dmaengine.h
> > index 4d0294ec3567..85afd71df2e7 100644
> > --- a/include/linux/dmaengine.h
> > +++ b/include/linux/dmaengine.h
> > @@ -643,6 +643,8 @@ struct dma_device {
> > int dev_id;
> > struct device *dev;
> >
> > + bool generic_slave_caps;
> > +
> > int (*device_alloc_chan_resources)(struct dma_chan *chan);
> > void (*device_free_chan_resources)(struct dma_chan *chan);
> >
> > @@ -772,17 +774,32 @@ static inline struct dma_async_tx_descriptor
> > *dmaengine_prep_interleaved_dma(
> >
> > static inline int dma_get_slave_caps(struct dma_chan *chan, struct
> > dma_slave_caps *caps) {
>
> This is getting too big for an inline function, it should be moved to
> drivers/dma/dmaengine.c.
I agree, but I wanted to do that in another patch set. This one is
just getting bigger and bigger, and this is not really the point of
this serie.
> > + struct dma_device *device;
> > +
> > if (!chan || !caps)
> > return -EINVAL;
> >
> > + device = chan->device;
> > +
> > /* check if the channel supports slave transactions */
> > - if (!test_bit(DMA_SLAVE, chan->device->cap_mask.bits))
> > + if (!test_bit(DMA_SLAVE, device->cap_mask.bits))
> > + return -ENXIO;
> > +
> > + if (device->device_slave_caps)
> > + return device->device_slave_caps(chan, caps);
> > +
> > + /*
> > + * Check whether it reports it uses the generic slave
> > + * capabilities, if not, that means it doesn't support any
> > + * kind of slave capabilities reporting.
> > + */
> > + if (device->generic_slave_caps)
> > return -ENXIO;
>
> Couldn't we replace that check with if (device->device_control) and get rid of
> the generic_slave_caps field ? Drivers converted to the new API would then get
> slave caps support for free.
Not really. Drivers might have converted to the splitted
device_control (and actually all of them are), while they don't define
the values needed to implement properly the generic slave caps
retrieval (and the vast majority of them doesn't).
Maxime
--
Maxime Ripard, Free Electrons
Embedded Linux, Kernel and Android engineering
http://free-electrons.com
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