Hi Maxime,
On Thursday 16 October 2014 18:24:53 Maxime Ripard wrote:
> On Thu, Oct 16, 2014 at 07:15:40PM +0300, Laurent Pinchart wrote:
> > 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.
If both get merged in the same kernel version I would be fine with this.
> > > + 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).
Indeed, my bad.
How about testing those fields then ? You could consider that the driver wants
the generic slave caps implementation if device->directions is set to a non-
zero value for instance.
--
Regards,
Laurent Pinchart
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