On Sunday 18 March 2012, Grant Likely wrote:
> > struct dma_channel *of_dma_request_channel(struct of_node*, int index,
> > dma_cap_mask_t *mask,
> > void *driver_data)
> > {
> > struct of_phandle_args dma_spec;
> > struct dma_device *device;
> > struct dma_chan *chan = NULL;
> > dma_filter_fn *filter;
> >
> > ret = of_parse_phandle_with_args(np, "dma-request", "#dma-cells",
> > index, &dma_spec);
> >
> > device = dma_find_device(dma_spec->np);
>
> Is dma_find_device() a new function? How does it look up the dma
> device?
Yes, it would be similar to the proposed function in Benoit's patch
> >
> > if (dma_spec->args_count == 0)
> > filter = dma_filter_simple;
> > else
> > filter = device->dma_dt_filter; /* new member */
>
> I'm not thrilled with this if/else hunk; even the case of
> #dma-cells=<0> should provide a hook; even it if is the stock simple
> filter. Leaving filter as NULL is the same as accepting everything
> anyway.
Right, good point. So a dmaengine driver would either register a trivial
filter if it wants to do anything here, or it would just leave it as a NULL
pointer otherwise.
Arnd
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