[alsa-devel] PATCH[1/1] Add I2S common driver for Intel MID platform

Liam Girdwood lrg at slimlogic.co.uk
Wed Oct 20 01:01:47 CEST 2010

On Tue, 2010-10-19 at 17:48 -0500, pl bossart wrote:
> >>         As this is used to transfer speech frames from/to cellular modem that have specific timing constraints (and modem also uses the I2S path to send some side-info), the Alsa SoC interface cannot be used.
> >
> > What makes you say this?  You have provided no detail on what problems
> > you believe exist and since ASoC is a *very* thin wrapper around the
> > core ALSA for DMA stuff it is very surprising that you would see any
> > issues here that don't also affect plain ALSA.  If there are any issues
> > then it would seem better to resolve these within the current framework
> > rather than completely discarding the entire existing infrastructure.
> Louis meant ALSA rather than ASOC. We use burst transfers to reduce
> round-trip delay, the whole notion of periods/period elapsed/ring
> buffer doesn't make sense here and there is in-band signalling that
> should not be interpreted as samples. If ALSA had a simplified API for
> byte streams sent over a serial output, we would have no problems
> using it and of course ASOC would be used then.

Is the inband signaling here done in software ? I'd expect this to be
multiplexed in the DAI by the hardware leaving the software to send PCM
bursts to the CODEC/MODEM/whatever like Peter's DAC33 driver.

Freelance Developer, SlimLogic Ltd
ASoC and Voltage Regulator Maintainer.

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