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From: Torsten Duwe <duwe@lst.de>
To: Harald Geyer <harald@ccbib.org>
Cc: Mark Rutland <mark.rutland@arm.com>,
	devicetree@vger.kernel.org, info@olimex.com,
	Maxime Ripard <maxime.ripard@bootlin.com>,
	Mark Brown <broonie@kernel.org>, Chen-Yu Tsai <wens@csie.org>,
	Rob Herring <robh+dt@kernel.org>,
	ibu@radempa.de, linux-arm-kernel@lists.infradead.org
Subject: Re: [PATCH RFC] arm64: dts: allwinner: a64: teres-i: Enable audio
Date: Sun, 17 Feb 2019 12:30:05 +0100
Message-ID: <20190217123005.6684abf9@blackhole.lan> (raw)
In-Reply-To: <E1gv6rh-0000Km-U8@stardust.g4.wien.funkfeuer.at>

On Sat, 16 Feb 2019 21:47:13 +0100
Harald Geyer <harald@ccbib.org> wrote:
> Torsten Duwe writes:

> > I consider the whole console
> > mux GPIO an U-Boot hack, and would put it into
> > sun50i-a64-teres-i-u-boot.dtsi. (As a LED, see above :-)
> 
> The thing is, one of the quite strict rules in kernel development is:
> Never break userspace. That means: If we provide a way to userspace to
> do something (ie switch between debug and audio), we are expected to
> keep it around forever.

No, that rule applies to mechanisms, not configuration. It's not a
problem if a device disappears completely, especially when it's
optional. For clarity's sake, imagine to drop a .dtbo on the fdt that
disables or removes it, after U-Boot has set it.

> > Would you care to submit a patch version without that GPIO handled?
> > I think it's very useful and has the potential to be agreed upon.
> 
> That would enable audio from the internal speakers but select debug
> output on the HP jack by default.

The kernel driver will use whatever the boot preset is; and a
production U-Boot should set that to audio.

> I would be okay with that, despite
> still thinking that audio on the head phones should be the default.

Yes, for production use. For kernel debugging, hack it in U-Boot.
The audio driver should be the last to care.

Imagine you are debugging a boot problem on the serial console and all
of a sudden it stops working just because the audio driver kicks in!

Should any driver ever be in control of that GPIO, it must not be
audio, IMO.

	Torsten


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Thread overview: 20+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
     [not found] <20190211111245.GA18147@lst.de>
2019-02-11 13:36 ` Harald Geyer
2019-02-11 15:39   ` Maxime Ripard
2019-02-11 19:32     ` Harald Geyer
2019-02-12  8:38       ` Maxime Ripard
2019-02-12  9:42         ` Harald Geyer
2019-02-12 10:09           ` Maxime Ripard
2019-02-12 19:37             ` Harald Geyer
2019-02-13  9:44               ` Maxime Ripard
2019-02-13 11:43                 ` Harald Geyer
2019-02-13 15:53                   ` Maxime Ripard
2019-02-14  0:12                     ` Harald Geyer
2019-02-15 14:20                       ` Torsten Duwe
2019-02-16 20:47                         ` Harald Geyer
2019-02-17 11:30                           ` Torsten Duwe [this message]
2019-02-18 10:24                           ` Maxime Ripard
2019-04-30 13:32                             ` Torsten Duwe
2019-05-02  7:46                               ` Maxime Ripard
2019-05-02 14:48                                 ` Harald Geyer
2019-02-01 11:37 Harald Geyer
2019-02-12  8:34 ` Chen-Yu Tsai

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