Messages in this thread | | | Date | Mon, 15 Jul 2013 20:51:45 +0100 | From | Mark Brown <> | Subject | Re: [RFC 1/2] ASoC: dmaengine-pcm: Add support for querying DMA capabilities |
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On Mon, Jul 15, 2013 at 08:20:28PM +0200, Lars-Peter Clausen wrote: > On 07/15/2013 07:57 PM, Mark Brown wrote: > >On Mon, Jul 15, 2013 at 10:27:21PM +0530, Vinod Koul wrote:
> >Right, we probably want to set an artificial floor here but it still > >seems like we should be checking that the device actually supports this. > >If the hardware can only support 64 bytes then the above code won't work > >properly.
> It shouldn't be to hard to extend the dma_caps API with a > min_sg_len. But is this something you've actually seen in existing > hardware for that the driver would make use of the dmaengine PCM > framework? If it is more of theoretical nature we can still easily > add it later if it becomes necessary.
I'm not aware of anything but equally well I made zero effort to look and note that quite a few existing drivers appear to have minimum values quite a bit above 16 though I doubt they are all actual restrictions.
> That said it is not uncommon that the segment size needs to be a > multiple of the burst size. Adding support for that is still on my > TODO list but will require some changes to some of the existing > users, since implementing this will be a lot easier if all users use > the snd_dmaengine_dai_dma_data struct for their DAI DMA data.
Yes, burst sizes are one source of restriction I've seen - probably the main one. [unhandled content-type:application/pgp-signature] | |