Re: [PATCH] dmaengine: Add hisilicon k3 DMA engine driver

[Vinod Koul <vinod.koul-ral2JQCrhuEAvxtiuMwx3w@public.gmane.org>]

On Mon, Jun 17, 2013 at 10:58:07PM +0200, Arnd Bergmann wrote:
> On Monday 17 June 2013, Zhangfei Gao wrote:
> > Add dmaengine driver for hisilicon k3 platform based on virt_dma
> > 
> > Signed-off-by: Zhangfei Gao <zhangfei.gao-QSEj5FYQhm4dnm+yROfE0A@public.gmane.org>
> > Tested-by: Kai Yang <jean.yangkai-hv44wF8Li93QT0dZR+AlfA@public.gmane.org>
> 
> Acked-by: Arnd Bergmann <arnd-r2nGTMty4D4@public.gmane.org>
> 
> 
> This filter function works only as long as there is no more than
> one DMA engine in the system, which is something that needs to
> be documented better. Unfortunately, providing a filter
> function to be called by .xlate is currently the only way that
> the dma-engine API supports, but we should really get over that.
> 
> Vinod: I think we need to add a way for a dmaengine driver to
> just return one of its channels to the xlate function. The
> current method is getting very silly, and it adds run-time and
> code complexity without any need.
> 
> How about something like
> 
> int dma_get_slave_channel(struct dma_chan *chan)
> {
> 	/* lock against __dma_request_channel */
> 	mutex_lock(&dma_list_mutex);
> 
> 	if (chan->client_count == 0)
> 		ret = dma_chan_get(chan);
> 	else	
> 		ret = -EBUSY;
> 
> 	mutex_unlock(&dma_list_mutex);
> 
> 	return ret;
> }
> EXPORT_SYMBOL_GPL(dma_get_slave_channel);
and you add filter on top?

This is getting you any channel and maynot work where we need to do some
filtering. 

--
~vinod
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