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Date: Tue, 19 Aug 2014 20:27:34 +0530
From: Vinod Koul <vinod.koul@intel.com>
To: Russell King - ARM Linux <linux@arm.linux.org.uk>,
        Dan Williams <dan.j.williams@intel.com>
Cc: Ludovic Desroches <ludovic.desroches@atmel.com>,
        Maxime Ripard <maxime.ripard@free-electrons.com>,
        Dan Williams <dan.j.williams@intel.com>, linux-kernel@vger.kernel.org,
        linux-arm-kernel@lists.infradead.org, dmaengine@vger.kernel.org,
        Arnd Bergmann <arnd@arndb.de>,
        Antoine =?iso-8859-1?Q?T=E9nart?= <antoine@free-electrons.com>,
        Thomas Petazzoni <thomas@free-electrons.com>,
        Alexandre Belloni <alexandre.belloni@free-electrons.com>,
        Boris Brezillon <boris@free-electrons.com>,
        Matt Porter <matt.porter@linaro.org>,
        laurent.pinchart@ideasonboard.com,
        Gregory Clement <gregory.clement@free-electrons.com>,
        Nicolas Ferre <nicolas.ferre@atmel.com>
Subject: Re: [PATCH] Documentation: dmaengine: Add a documentation for the
 dma controller API
Message-ID: <20140819145734.GN13288@intel.com>
References: <1406736193-26685-1-git-send-email-maxime.ripard@free-electrons.com>
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 <20140814085753.GS30401@n2100.arm.linux.org.uk>
 <20140819134507.GJ13288@intel.com>
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On Tue, Aug 19, 2014 at 03:44:23PM +0100, Russell King - ARM Linux wrote:
> On Tue, Aug 19, 2014 at 07:15:07PM +0530, Vinod Koul wrote:
> > On Thu, Aug 14, 2014 at 09:57:53AM +0100, Russell King - ARM Linux wrote:
> > > It's got something to do with the async engine API, and seems to be
> > > something to do with whether a descriptor can have other transactions
> > > added to it, and whether a descriptor can be re-used (async-tx engines
> > > typically allocate a fixed set of descriptors and recycle them.)
> > Yes this is my understanding too. Async API IIUC can reuse descriptors and
> > if engine doesnt support this is a way to tell them please do use that.
> > 
> > For slave dmanegine API we need to ignore it.
> 
> We shouldn't ignore it - ignoring it makes it harder to implement a DMA
> engine driver which supports both the slave and async APIs, because
> we then need to know the reason for the channel being requested.
Do you have such usage coming up near future :)
> 
> Ignoring it until it can be understood and documented is an approach I
> would agree with though.
Certainly, I am asking Dan to add more clarity on these bits to help
improve.

-- 
~Vinod