linux-kernel - Re: [PATCH 2/3] ARM: edma: Rename header file for dmaengine filter function definition

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Date:	Thu, 27 Nov 2014 15:50:46 +0100
From:	Arnd Bergmann <arnd@...db.de>
To:	linux-arm-kernel@...ts.infradead.org
Cc:	Peter Ujfalusi <peter.ujfalusi@...com>,
	alsa-devel@...a-project.org, linux-omap@...r.kernel.org,
	linux@....linux.org.uk, vinod.koul@...el.com,
	linux-mmc@...r.kernel.org, nsekhar@...com,
	Liam Girdwood <lgirdwood@...il.com>,
	linux-kernel@...r.kernel.org, khilman@...prootsystems.com,
	Tony Lindgren <tony@...mide.com>,
	Mark Brown <broonie@...nel.org>, chris@...ntf.net,
	dmaengine@...r.kernel.org, ulf.hansson@...aro.org,
	linux-spi@...r.kernel.org
Subject: Re: [PATCH 2/3] ARM: edma: Rename header file for dmaengine filter function definition

On Thursday 27 November 2014 16:23:31 Peter Ujfalusi wrote:
> This will only work in case of legacy boot. When booting with DT we do not
> have pdata and after this patch in dt boot we are not going to be able to get
> the DMA resources either.

No, when booting with DT, the filter_fn and data are not used at all,
we get the dma channel by parsing the DT instead.

> I think if we want to do something like this, it has to be done within the
> dmaengine framework. The dma controller's of_dma_filter_info already have
> .filter_fn which could be used by the framework.

No, of_dma_filter_info/of_dma_simple_xlate was a mistake, we should never
have even introduced that. All drivers that rely on this can simply
provide their own xlate function that calls of_dma_get_slave_channel()
or one of the related functions.

edma is particularly trivial, it can just use of_dma_xlate_by_chan_id()
instead of of_dma_simple_xlate, as it looks up the channel by its number.

	Arnd
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