Re: [PATCH/RFC] dmaengine: add a slave parameter to __dma_request_channel()

From: Vinod Koul <vinod.koul@intel.com>
To: Guennadi Liakhovetski <g.liakhovetski@gmx.de>
Cc: Russell King - ARM Linux <linux@arm.linux.org.uk>,
	linux-kernel@vger.kernel.org,
	"'Jassi Brar'" <jassisinghbrar@gmail.com>,
	Linus Walleij <linus.walleij@linaro.org>,
	Magnus Damm <magnus.damm@gmail.com>,
	Paul Mundt <lethal@linux-sh.org>
Subject: Re: [PATCH/RFC] dmaengine: add a slave parameter to __dma_request_channel()
Date: Fri, 09 Mar 2012 14:51:58 +0530	[thread overview]
Message-ID: <1331284918.4657.69.camel@vkoul-udesk3> (raw)
In-Reply-To: <Pine.LNX.4.64.1203081412550.29847@axis700.grange>

On Thu, 2012-03-08 at 14:18 +0100, Guennadi Liakhovetski wrote:
> > Assuming I didn't miss...
> > 
> > The case B can be handled without sweat by platforms channel mapping
> > information.
> > 
> > Case A where we don't find that devices exist in map, thus being treated
> > as generic DMA channels and can be handled easily in sequence. So when
> > someone in Q request a channel it would get first channel in Ps
> > 
> > This way we handle both of them in a transparent manner to both clients
> > and controllers. 
> > 
> > Perhaps we can also add capability to know that if channel is to be
> > searched in map or not - would be anyway required for non slave cases.
> 
> Right, but I don't understand then what this gives us. You propose some 
> channel maps, that will not be used for your "case A." Which means, for 
> "case A" nothing changes. So, the reason for this whole thread hasn't been 
> addressed: how to pass channel configuration to the DMA controller driver.
For "Case A" there should be no filtering or any issues even now. You
have controller requesting a channel and as long as they get a channel
for respective pool, it should work.

Or is there anything else which is required in this case?

-- 
~Vinod