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Date:   Tue, 29 Dec 2020 13:06:57 +0000
From:   Charles Keepax <ckeepax@opensource.cirrus.com>
To:     Mark Brown <broonie@kernel.org>
CC:     Hans de Goede <hdegoede@redhat.com>,
        Lee Jones <lee.jones@linaro.org>,
        MyungJoo Ham <myungjoo.ham@samsung.com>,
        Chanwoo Choi <cw00.choi@samsung.com>,
        Cezary Rojewski <cezary.rojewski@intel.com>,
        Pierre-Louis Bossart <pierre-louis.bossart@linux.intel.com>,
        Liam Girdwood <liam.r.girdwood@linux.intel.com>,
        Jie Yang <yang.jie@linux.intel.com>,
        <patches@opensource.cirrus.com>, <linux-kernel@vger.kernel.org>,
        <alsa-devel@alsa-project.org>
Subject: Re: [PATCH 01/14] mfd: arizona: Add jack pointer to struct arizona
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On Mon, Dec 28, 2020 at 04:28:07PM +0000, Mark Brown wrote:
> On Mon, Dec 28, 2020 at 02:16:04PM +0100, Hans de Goede wrote:
> 
> > And more in general AFAIK extcon is sort of deprecated and it is
> > not advised to use it for new code. I would esp. not expect it to
> > be used for new jack-detection code since we already have standard
> > uAPI support for that through sound/core/jack.c .
> 
> Has Android been fixed to use the ALSA/input layer interfaces?  That's
> why that code is there, long term the goal was to have ALSA generate
> extcon events too so userspace could fall over to using that.  The basic
> thing at the time was that nobody liked any of the existing interfaces
> (the input layer thing is a total bodge stemming from it having been
> easy to hack in a key for GPIO detection and using ALSA controls means
> having to link against alsa-lib which is an awful faff for system level
> UI stuff) and there were three separate userspace interfaces used by
> different software stacks which needed to be joined together, extcon was
> felt to be a bit more designed and is a superset so that was the
> direction we were heading in.

Android has been updated to have the option to catch input events
for jack detection now.

I have always been slightly confused between extcon and the ALSA
jack reporting and have been unsure as to what is the longer term
plan here. I vaguely thought there was a gentle plan to move to
extcon, it is interesting to see Hans basically saying the
opposite that extcon is intended to be paritially deprecated. I
assume you just mean with respect to audio jacks, not other
connector types?

I would agree with Mark though that if extcon exists for external
connectors it seems odd that audio jacks would have their own
special way rather than just using the connector stuff.

Thanks,
Charles