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 :) -- ~Vinod > > Not doing this implies that if you have a half-duplex device, you have to > repeatedly issue a dmaengine_slave_config() call, a prepare call, and a > submit call to the DMA engine code for every segment you want to transfer. > We don't need that kind of DMA engine specific behaviour in DMA engine > users. > > -- > FTTC broadband for 0.8mile line: 5.8Mbps down 500kbps up. Estimation > in database were 13.1 to 19Mbit for a good line, about 7.5+ for a bad. > Estimate before purchase was "up to 13.2Mbit". > -- > To unsubscribe from this list: send the line "unsubscribe dmaengine" in > the body of a message to majordomo@xxxxxxxxxxxxxxx > More majordomo info at http://vger.kernel.org/majordomo-info.html -- -- To unsubscribe from this list: send the line "unsubscribe devicetree" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
