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 [thread overview]
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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next prev parent reply other threads:[~2019-02-17 11:30 UTC|newest]
Thread overview: 20+ messages / expand[flat|nested] mbox.gz Atom feed top
[not found] <20190211111245.GA18147@lst.de>
2019-02-11 13:36 ` [PATCH RFC] arm64: dts: allwinner: a64: teres-i: Enable audio 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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