Re: [PATCH] DMA: let filter functions of of_dma_simple_xlate possible check of_node

Laurent Pinchart
2013-08-26T12:17:43Z

On Friday 23 August 2013 09:57:43 Stephen Warren wrote:
> On 08/22/2013 07:29 PM, Richard Zhao wrote:
> > On Fri, Aug 23, 2013 at 04:18:27AM +0800, Stephen Warren wrote:
> >> On 08/21/2013 11:19 PM, Richard Zhao wrote:
> >>> On Fri, Aug 02, 2013 at 10:00:00AM +0800, Richard Zhao wrote:
> >>>> pass of_phandle_args dma_spec to dma_request_channel in
> >>>> of_dma_simple_xlate, so the filter function could access of_node in
> >>>> of_phandle_args.
> >>>>
> >>>> It also remove restriction of #dma-cells has to be one.
> >>>>
> >>>> Signed-off-by: Richard Zhao <rizhao@nvidia.com>
> >>>> ---
> >>>>
> >>>> drivers/dma/edma.c | 7 +++++--
> >>>> drivers/dma/of-dma.c | 10 ++++------
> >>>> drivers/dma/omap-dma.c | 6 ++++--
> >>>> 3 files changed, 13 insertions(+), 10 deletions(-)
> >>>
> >>> Hi Vinod,
> >>>
> >>> Can you please pick up this change?
> >>>
> >>> Hi Stephen,
> >>>
> >>> Can you please give a ack or reviewed-by etc?
> >>
> >> Hmm. Looking at the patch, I'm not sure it's right.
> >>
> >> This patch simply passes all the specfier args to the filter function,
> >> and the code to check the equality of the of_node to the filter args is
> >> still duplicated in each DMA driver. Instead, the DMA core should be
> >> implementing the equality check, and only even calling the
> >> driver-specific filter function for devices where the client's phandle
> >> matches the DMA providing device's of_node handle.
> >
> > Filter function is called in dmaengine core code, independent of dt.
>
> The core code can still check if a dmaengine's driver was instantiated
> from DT and take additional actions in that case.
>
> > And the reason why the driver has to write its own filter function is
> > it has to store slave id there in its own way.
>
> I'm not saying don't call the driver's filter function, but rather that
> the dmaengine core should perform the common checks before doing so.

And it looks to me like the common case could even get rid of the driver's
filter function:

https://lkml.org/lkml/2013/5/15/270
https://lkml.org/lkml/2013/3/25/250

--
Regards,

Laurent Pinchart