On 27/02/17 19:04, Matthias Reichl wrote:
On Mon, Feb 27, 2017 at 09:35:14AM +1100, Matt Flax wrote:
On 27/02/17 09:16, Matthias Reichl wrote:
Have a look at the end of Documentation/sound/alsa/soc/DPCM.txt
where codec<->codec links are explained.
You can setup the stream parameters for the "IC"<->"real codec" link
with snd_soc_dai_link.params.
You can do that for example in your machine driver in hwparams:
when hw_params is called eg with 2 channels 192kHz just set the
dai link parameters of the codec to 8 channels 48kHz.
Maybe using dynamic pcm (which offers a be_hw_params_fixup hook)
is the more appropriate way to do that, but I can't tell for sure
as I never used it and am not familiar with it.
Thanks for this information, I will give this a go - seems a better way now
then introducing an IC master into the mix !
Do you agree that we still need the BCM2835 SoC CPU driver to be expanded to
handle DSP mode
and multichannel setups ? I can't see any other way to enable the
multichannel hardware setup without altering bcm2835_i2s.c to handle DSP
mode and more then 2 channels in its _hw_params.
No, DSP mode and multichannel don't work on the BCM2835. Keep the driver
as it is.
Use the alsa plugin approach to tunnel multichannel data over a 2-channel
PCM and you don't need to modify existing drivers.
Thanks again for this suggestion. I have been playing around with user
space plugins lately, they are great. I plan to release some C++ classes
to help trivialise the creation of such plugins.
However for a product, a piece of robustly functioning hardware, I am
inclined to take the route of introducing a DSP mode into the
bcm2835_i2s.c driver.
From the previous patches, it is clear that people are willing to allow
multichannel (DSP mode) into the bcm2835 CPU driver. It improves the
usefulness of hardware which use the BCM2835 derived chipset. From my
point of view that is a major simplification in terms of releasing
functioning multichannel hardware. I would imagine from the
manufacturer's point of view that is a big bonus too !
Again I intend to implement your concept of the snd_soc_dai_link for my
machine driver, that is a fantasic lead you have given me ... when I
have questions @ implementation time I will copy you in seeking for more
guidance.
thanks again,
Matt
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