linux-kernel - Re: [PATCH RESEND 1/2] regulator: Add support for parsing operation mode

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Message-ID: <20160511144632.GH6261@sirena.org.uk>
Date:	Wed, 11 May 2016 15:46:32 +0100
From:	Mark Brown <broonie@...nel.org>
To:	Henry Chen <henryc.chen@...iatek.com>
Cc:	Rob Herring <robh+dt@...nel.org>,
	Liam Girdwood <lgirdwood@...il.com>,
	Matthias Brugger <matthias.bgg@...il.com>,
	Pawel Moll <pawel.moll@....com>,
	Mark Rutland <mark.rutland@....com>,
	Ian Campbell <ijc+devicetree@...lion.org.uk>,
	Kumar Gala <galak@...eaurora.org>,
	Stephen Boyd <sboyd@...eaurora.org>,
	Bjorn Andersson <bjorn.andersson@...ymobile.com>,
	Laxman Dewangan <ldewangan@...dia.com>,
	devicetree@...r.kernel.org, linux-kernel@...r.kernel.org,
	linux-arm-kernel@...ts.infradead.org,
	linux-mediatek@...ts.infradead.org
Subject: Re: [PATCH RESEND 1/2] regulator: Add support for parsing operation
 mode

On Wed, May 11, 2016 at 05:31:29PM +0800, Henry Chen wrote:

> +- regulator-allow-change-mode: allow the regulator mode to be configured
> +- regulator-supported-modes: Regulators can run in a variety of different operating
> +  modes depending on output load. This allows further system power savings by
> +  selecting the best (and most efficient) regulator mode for a desired load.
> +  The definition for each of these operation is defined at
> +  include/linux/regulator/consumer.h

It really isn't OK for a DT binding to be documented by referencing
Linux kernel internals.

> +	0: FAST.
> +	1: NORMAL.
> +	2: IDLE.
> +	3: STANDBY.

The problem with these is that they don't really mean anything outside
of a specific regulator.  This makes it very hard to make them at all
interoperable, and is also incompatible with the way we're currently
handling the modes elsewhere in the bindings.  If we're going to make an
ABI of this we need to have something with abstraction in it but it's
hard to see how to abstract modes since they're so implementation
specific, even if the mechanisms are similar the different load ranges
that regulators support mean that what's a very taxing load for one
regulator may be nothing to another.

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