linux-kernel - Re: [PATCH] DMA: let filter functions of of_dma_simple_xlate possible check of

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Message-ID: <1441310.1kjKG7uebg@avalon>
Date:	Mon, 26 Aug 2013 14:17:43 +0200
From:	Laurent Pinchart <laurent.pinchart@...asonboard.com>
To:	Stephen Warren <swarren@...dotorg.org>
Cc:	Richard Zhao <rizhao@...dia.com>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	"linux-omap@...r.kernel.org" <linux-omap@...r.kernel.org>,
	"linux-arm-kernel@...ts.infradead.org" 
	<linux-arm-kernel@...ts.infradead.org>,
	"vinod.koul@...el.com" <vinod.koul@...el.com>,
	"djbw@...com" <djbw@...com>
Subject: Re: [PATCH] DMA: let filter functions of of_dma_simple_xlate possible check of_node

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@...dia.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

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