On Tuesday 18 June 2013, zhangfei gao wrote: > On Tue, Jun 18, 2013 at 4:58 AM, Arnd Bergmann <a...@arndb.de> wrote: > > > >> +static struct of_dma_filter_info k3_dma_filter; > >> +static bool k3_dma_filter_fn(struct dma_chan *chan, void *param) > >> +{ > >> + return (*(int *)param == chan->chan_id); > >> +} > > > > 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); > > Want to double check here. > Device need specific channel via request line, the requirement still > can be met, right?
The driver can have a simple array of pointers that is indexed by the request number, so you end up with something like struct dma_chan *of_dma_simple_xlate(struct of_phandle_args *dma_spec, struct of_dma *ofdma) { struct k3_dma_dev *dev = ofdma->of_dma_data; unsigned int vchan = dma_spec->args[0]; if (vchan > dev->nr_channels) return NULL; return dma_get_slave_channel(dev->vchan[vchan]); } With no need to have a filter function. Arnd _______________________________________________ devicetree-discuss mailing list devicetree-discuss@lists.ozlabs.org https://lists.ozlabs.org/listinfo/devicetree-discuss