[alsa-devel] [PATCH 1/4] DMA: PL330: Add xlate function

[Padma Venkat]

Hi,

On Mon, Jan 28, 2013 at 8:28 PM, Arnd Bergmann <arnd at arndb.de> wrote:
> On Friday 18 January 2013, Padmavathi Venna wrote:
>> +struct dma_chan *of_dma_pl330_xlate(struct of_phandle_args *dma_spec,
>> +                                               struct of_dma *ofdma)
>> +{
>> +       int count = dma_spec->args_count;
>> +       struct of_dma_filter_info *info = ofdma->of_dma_data;
>> +
>> +       if (!info || !info->filter_fn)
>> +               return NULL;
>> +
>> +       if (count != 1)
>> +               return NULL;
>> +
>> +       return dma_request_channel(info->dma_cap, info->filter_fn, dma_spec);
>> +}
>> +EXPORT_SYMBOL_GPL(of_dma_pl330_xlate);
>
> It seems a little sad that we still have to use dma_request_channel()
> to implement this, when that function will go off searching all channels
> and pass them tino the filter, which then has to look for the device node
> and match it with each channel. We already know the controller and should
> just be able to get a channel for it, although I don't exactly know how
> that is done.
>
> Further, your function is almost identical to the of_dma_simple_xlate
> function. Can't you use that one instead?

of_dma_simple_xlate is just passing the dma channel number to the
filter function. But I also need
to compare against device node as my requested channel can belong to
any of the available dma controller
on SoC. So I implemented a xlate which passes the whole dma_spec.

Thanks for reviewing the patches.

Regards
Padma

>
>         Arnd