linux-kernel - Re: [PATCH 1/1] mmc: core: Use regulator_get

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Message-ID: <20140815095528.GH17528@sirena.org.uk>
Date:	Fri, 15 Aug 2014 10:55:28 +0100
From:	Mark Brown <broonie@...nel.org>
To:	Javier Martinez Canillas <javier.martinez@...labora.co.uk>
Cc:	Tim Kryger <tim.kryger@...il.com>,
	Ulf Hansson <ulf.hansson@...aro.org>,
	Chris Ball <chris@...ntf.net>,
	Seungwon Jeon <tgih.jun@...sung.com>,
	Haijun Zhang <Haijun.Zhang@...escale.com>,
	Doug Anderson <dianders@...omium.org>,
	Olof Johansson <olof@...om.net>,
	Yuvaraj Kumar C D <yuvaraj.cd@...il.com>,
	linux-samsung-soc <linux-samsung-soc@...r.kernel.org>,
	linux-mmc <linux-mmc@...r.kernel.org>,
	Linux Kernel Mailing List <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH 1/1] mmc: core: Use regulator_get_voltage() if OCR mask
 is empty.

On Fri, Aug 15, 2014 at 09:48:43AM +0200, Javier Martinez Canillas wrote:

> But now I wonder why regulator_list_voltage() even list the voltage for
> fixed regulators (desc->fixed_uV) since they don't have the ability to
> vary voltage. The regulator_list_voltage() documentation says:

That's because it's very cheap to do and there is a comprehensible thing
we can return - if we have to read the voltage that means potentially
asking the hardware in an I2C transaction which is not cheap.

> > It seems odd to make callers be the ones to handle this subtlety.

> If regulator_list_voltage() didn't list the voltage for fixed regulators,
> then this subtlety should had been handled by callers before but they
> didn't because they rely on regulator_list_voltage() to always return a
> voltage even for fixed regulators.

There's plenty of potentially variable regulators used in these
situations, I expect it's more likely that people were just ignoring the
warning since it has no practical effect.

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