On Fri, Feb 03, 2012 at 03:05:12PM +0100, Lars-Peter Clausen wrote:
Yes, I was faced with the task of writing yet another dmaengine based ASoC PCM driver last week. At first I thought it might be a good idea to come up with a common ASoC PCM driver which could be used by all platforms using DMA engine. Unfortunately this turned out to be not feasible due to how dmaengine works. Each dmaengine driver has it's custom API for configuring the DMA controller. :/
That doesn't sound insurmountible - you need a callback to allow the individual drivers to set the parameters but hopefully the data flow is more generic? There will probably be some other setup type stuff that needs doing.
The other ASoC platforms using dmaengine for their PCM driver (including the one in this patch series) don't have this function implemented and so the PCM drivers manually have to setup the cyclic SG lists. So while we could add a common set up functions for this to ASoC or ALSA I think the better place for this is in the dmaengine framework and implement device_prep_dma_cyclic for those drivers which don't do yet.
That seems like a good plan, that way other users of cyclic DMA will also benefit.