linux-kernel - Re: handling voice calls in ALSA soc (on Droid 4)

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Date:   Tue, 12 Jun 2018 14:18:03 +0200
From:   Pavel Machek <pavel@....cz>
To:     Mark Brown <broonie@...nel.org>
Cc:     kernel list <linux-kernel@...r.kernel.org>,
        linux-arm-kernel <linux-arm-kernel@...ts.infradead.org>,
        linux-omap@...r.kernel.org, tony@...mide.com, sre@...nel.org,
        nekit1000@...il.com, mpartap@....net, merlijn@...zup.org,
        alsa-devel@...a-project.org, tiwai@...e.com, perex@...ex.cz,
        lgirdwood@...il.com
Subject: Re: handling voice calls in ALSA soc (on Droid 4)

Hi!

Sebastian, would you have pointer to original Motorola sources you
used for inspiration?

> > With setup like that, how does userland tell kernel that the baseband
> > <-> microphone/speaker connection should be activated?
> 
> Audio routing should be done as normal, and ideally the driver for the
> modem will be able to figure out if there's an active call or not.  If
> userspace has to enable the input and output manually then you can set
> up SOC_DAPM_PIN_SWITCH()es as normal.

Modem talks AT commands, so the driver is in userspace for now.

I tried SOC_DAPM_PIN_SWITCH(), but it results in alsamixer oopsing, I
guess I'm doing something wrong.

Message from syslogd@...uan at Jun 12 13:51:31 ...
 kernel:[  743.678588] BUG: spinlock bad magic on CPU#1,
 alsamixer/2217

Message from syslogd@...uan at Jun 12 13:51:31 ...
 kernel:[  743.684417]  lock: 0xede423a0, .magic: eee2a6a4, .owner:
 <none>/-1, .owner_cpu: -287136604
 
I'm trying to understand how it is supposed to work, but
https://www.alsa-project.org/main/index.php/DAPM has TODO's at
critical places. If there's better source of information, let me know.

Best regards,
									Pavel
-- 
(english) http://www.livejournal.com/~pavelmachek
(cesky, pictures) http://atrey.karlin.mff.cuni.cz/~pavel/picture/horses/blog.html

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