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.) 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 devicetree" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
