On 11/26/2013 02:25 AM, Stephen Warren wrote:
[...]
> +struct dma_chan *of_dma_slave_xlate(struct of_phandle_args *dma_spec,
> + struct of_dma *ofdma)
> +{
> + struct of_dma_slave_xlate_info *info = ofdma->of_dma_data;
> + struct dma_chan *candidate, *chan;
> + int ret;
> +
> +retry:
> + candidate = NULL;
> +
> + /*
> + * walk the list of channels registered with the current instance and
> + * find one that is currently unused
> + */
> + list_for_each_entry(chan, &info->device->channels, device_node)
> + if (chan->client_count == 0) {
> + candidate = chan;
> + break;
> + }
> +
> + if (!candidate)
> + return NULL;
> +
> + /*
> + * dma_get_slave_channel will return NULL if we lost a race between
> + * the lookup and the reservation
> + */
> + chan = dma_get_slave_channel(candidate);
> + if (!chan)
> + goto retry;
I think it will be better to implement this functionality in the core. This
means we can hold the dma_list_mutex and don't have to do this retry loop
and do not have to peek at the client_count field in non-core code.
Something like dma_get_free_slave_channel(), which would call
private_candidate() followed by dma_chan_get().
> +
> + if (info->post_alloc) {
> + ret = info->post_alloc(chan, dma_spec);
If you need to do something at the end of the function I think it is nicer
to just wrap this function with your own function instead of adding a callback.
- Lars
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