From: Vinod Koul <vinod.koul@intel.com>
To: Guennadi Liakhovetski <g.liakhovetski@gmx.de>
Cc: Alexandre Bounine <alexandre.bounine@idt.com>,
akpm@linux-foundation.org, linux-kernel@vger.kernel.org,
linuxppc-dev@lists.ozlabs.org, dan.j.williams@intel.com,
Jassi Brar <jaswinder.singh@linaro.org>,
Russell King <rmk@arm.linux.org.uk>,
Kumar Gala <galak@kernel.crashing.org>,
Matt Porter <mporter@kernel.crashing.org>,
Li Yang <leoli@freescale.com>
Subject: Re: [RFC] dmaengine/dma_slave: add context parameter to prep_slave_sg callback
Date: Wed, 01 Feb 2012 20:09:35 +0530 [thread overview]
Message-ID: <1328107175.1610.32.camel@vkoul-udesk3> (raw)
In-Reply-To: <Pine.LNX.4.64.1202011234180.24739@axis700.grange>
On Wed, 2012-02-01 at 12:58 +0100, Guennadi Liakhovetski wrote:
> > The two things are completely orthogonal and shouldn't be clubbed.
> > For your issue we need a separate debate on how to solve this... I am
> > open to ideas...
>
> Well, I'm not sure whether they are necessarily always orthogonal, they
> don't seem so in my case at least. We definitely can use our approach -
> configure the channel during allocation. I _think_ we could also perform
> the configuration on a per-transfer basis, during the prepare stage, as
> this RFC is suggesting, but that definitely would require reworking the
> driver somewhat and changing the concept. The current concept is a fixed
> DMA channel allocation to slaves for as long as the slave is using DMA.
> This is simpler, avoids some overhead during operation and fits well with
> the dmaengine PRIVATE channel concept. So, given the choice, we would
> prefer to perform the configuration during channel allocation.
>
> Maybe there are cases, where the driver absolutely needs this additional
> information during allocation, in which case my proposal would be the only
> way to go for them.
what are you trying to address, sending controller specific information
at allocation or the channel allocation itself. I kind of sense both.
But apprach here is discussed is to pass paramters which are required
for each transfer, not static for a channel, hence the additional
controller specific parameter in respective prepare.
>
> I'll post an RFC soon - stay tuned:-)
Patch is always the best idea :-)
--
~Vinod
prev parent reply other threads:[~2012-02-01 14:38 UTC|newest]
Thread overview: 8+ messages / expand[flat|nested] mbox.gz Atom feed top
2012-01-26 21:22 [RFC] dmaengine/dma_slave: add context parameter to prep_slave_sg callback Alexandre Bounine
2012-01-30 9:30 ` Vinod Koul
2012-01-30 16:55 ` Bounine, Alexandre
2012-01-31 3:14 ` Vinod Koul
2012-02-01 0:09 ` Guennadi Liakhovetski
2012-02-01 5:43 ` Vinod Koul
2012-02-01 11:58 ` Guennadi Liakhovetski
2012-02-01 14:39 ` Vinod Koul [this message]
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