Re: [Ksummit-discuss] [CORE TOPIC] Mainline kernel on a cellphone

[Pavel Machek <pavel@ucw.cz>]

On Wed 2015-07-29 14:32:44, Mark Brown wrote:
> On Thu, Jul 23, 2015 at 10:29:02PM +0200, Pavel Machek wrote:
> 
> > 4) voice link to modem: Nokia people tell us that ALSA is not suitable
> > interface to modem audio. What is the right interface, then?
> 
> ALSA is the right interface for this, this is going to be some
> misunderstanding on their part about how to use it or limitations in

That's what I was arguing, but see https://lkml.org/lkml/2015/3/5/606
.

kai> Our take was that ALSA is not the right interface for cmt_speech. The
kai> cmt_speech interface in the modem is _not_ a PCM interface as modelled
kai> by
kai> ALSA. Specifically:
kai>
kai>- the interface is lossy in both directions
kai>- data is sent in packets, not a stream of samples (could be other
kai>- things
kai>   than PCM samples), with timing and meta-data
kai>   - timing of uplink is of utmost importance
   

> the drivers for their particular system (and possibly some unfortunate
> hardware design, it sounds like they may still be bouncing the voice
> call through the AP which isn't the most wonderful idea ever).
> There

Actually, sending data through AP is _very_ good idea from security
perspective. You don't want hacked baseband to eavesdrop on you, do
you?

Best regards,
									Pavel

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