linux-kernel - Re: [PATCH] serial: sh-sci: don't filter on DMA device, use only channel ID

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Date:	Fri, 09 Sep 2011 01:01:03 +0530
From:	Vinod Koul <vkoul@...radead.org>
To:	Paul Mundt <lethal@...ux-sh.org>
Cc:	vinod.koul@...el.com,
	"g.liakhovetski@....de" <g.liakhovetski@....de>,
	"Williams, Dan J" <dan.j.williams@...el.com>,
	"magnus.damm@...il.com" <magnus.damm@...il.com>,
	"linux-sh@...r.kernel.org" <linux-sh@...r.kernel.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	"damm@...nsource.se" <damm@...nsource.se>
Subject: Re: [PATCH] serial: sh-sci: don't filter on DMA device, use only
 channel ID

On Thu, 2011-09-08 at 10:21 +0900, Paul Mundt wrote:
> On Thu, Sep 08, 2011 at 03:07:53AM +0530, Koul, Vinod wrote:
> > On Wed, 2011-09-07 at 22:01 +0200, Guennadi Liakhovetski wrote:
> > > On Thu, 8 Sep 2011, Koul, Vinod wrote:
> > > You're seriously suggesting to export and use an additional shdma private 
> > > function, bypassing the dmaengine API?... That really doesn't sound like a 
> > > good idea to me, sorry. How about using .device_control(DMA_SLAVE_CONFIG) 
> > > from the filter function directly to verify channel suitability?
> > Yes see stedma40, coh90138 drivers
> > .device_control is not right place as channel is already allocated.
> > 
> 
> No, that's not going to happen either. Many of these drivers are used in
> different CPUs with different DMACs. The dmaengine driver in question
> only applies to a subset, so the driver bits need to be wholly generic.
> In short, if the dmaengine API can't handle this sort of stuff then it's
> the dmaengine API that needs to be extended, we won't be working around
> dmaengine shortcomings in drivers that simply want a sensible DMA API to
> plug in to.The only thing lacking in dmaengine API is proper filtering for slave
usages where channel/controller is matches to specfic dmac slave.

There was a proposal by Linux W, and Jassi Brar for solving this
problem, and I think that should solve above problem.

I relooked at the patch, since the filtering is already done in
your .alloc_chan_resources, (which should be fixed when we fix
filtering), I am going to apply this patch


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