On Mon, Nov 25, 2013 at 11:40 PM, Lars-Peter Clausen <l...@metafoo.de> wrote:
> 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.
>
Agree with both points above. And if the common pattern is to limit
the domain to children of a given parent device that can be
implemented generically with a device_for_each_child_loop or similar.
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