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Date: Tue, 28 Jan 2014 13:08:47 +0100 From: Arnd Bergmann <arnd@...db.de> To: Vinod Koul <vinod.koul@...el.com> Cc: Russell King - ARM Linux <linux@....linux.org.uk>, Lars-Peter Clausen <lars@...afoo.de>, devicetree@...r.kernel.org, linux-arm-msm@...r.kernel.org, linux-kernel@...r.kernel.org, Andy Gross <agross@...eaurora.org>, dmaengine@...r.kernel.org, Dan Williams <dan.j.williams@...el.com>, linux-arm-kernel@...ts.infradead.org Subject: Re: [Patch v3 2/2] dmaengine: qcom_bam_dma: Add device tree binding On Tuesday 28 January 2014 13:05:10 Arnd Bergmann wrote: > On Tuesday 28 January 2014 17:02:42 Vinod Koul wrote: > > On Tue, Jan 28, 2014 at 11:17:57AM +0000, Russell King - ARM Linux wrote: > > > On Tue, Jan 28, 2014 at 10:16:53AM +0100, Arnd Bergmann wrote: > > > > On Tuesday 28 January 2014 10:05:35 Lars-Peter Clausen wrote: > > > > > Why does the direction needs to be specified in specifier? I see two > > > > > options, either the direction per is fixed in hardware. In that case the DMA > > > > > controller node should describe which channel is which direction. Or the > > > > > direction is not fixed in hardware and can be changed at runtime in which > > > > > case it should be set on a per descriptor basis. > > > > > > > > Normally the direction is implied by dmaengine_slave_config(). > > > > > > No. The direction argument in there is deprecated - we've been talking > > > about removing it for some time. > > > > > > DMA engine drivers should store all parameters of the configuration, and > > > then select the appropriate ones when preparing a transfer (which itself > > > involves a direction.) > > > > Right all the prep_ calls for slave cases have explcit direction argument so > > sending it using slave config makes no sense. So will remove it after the merge > > window closes and fix > > Ok, thanks for clearing up my mistake. However, the argument remains: > the direction doesn't need to be in the DT DMA descriptor since it > gets set by software anyway. On a related note, should we try to remove the slave_id field from the slave config structure as well? I believe it is still used by the shmobile dma engine in non-DT mode, but that is inconsistent with how all the others work, and with what the same driver does for DT. Arnd -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@...r.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
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