linux-kernel - Re: [PATCH] sdhci: Forward EPROBE_DEFER on vmmc and vqmmc regulators

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Date:	Wed, 16 Apr 2014 21:47:33 +0100
From:	Mark Brown <broonie@...nel.org>
To:	Andrew Bresticker <abrestic@...omium.org>
Cc:	Mike Looijmans <mike.looijmans@...ic.nl>,
	Arnd Bergmann <arnd@...db.de>,
	Ben Dooks <ben.dooks@...ethink.co.uk>,
	"linux-mmc@...r.kernel.org" <linux-mmc@...r.kernel.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	cjb@...top.org, gdjakov@...sol.com
Subject: Re: [PATCH] sdhci: Forward EPROBE_DEFER on vmmc and vqmmc regulators

On Wed, Apr 16, 2014 at 01:15:53PM -0700, Andrew Bresticker wrote:

> Not true.  If !CONFIG_REGULATOR, regulator_get() and co. will return
> NULL.  Normally it is ok to ignore this case, but the sdhci driver
> will call regulator_is_supported_voltage() on vqmmc to determine
> whether 1.8V signalling is supported.  With !CONFIG_REGULATOR,
> regulator_is_supported_voltage() will always return false, causing the
> sdhci driver to disable all UHS modes.  So we still need to handle the
> NULL (!CONFIG_REGULATOR) case.  One possibility is to guard the
> voltage check with #ifdef CONFIG_REGULATOR, as is done later with
> vmmc.

It seems better to just fix regulator_get_optional() to return an error
if the API is disabled, that case didn't really get considered since
it's a bit surprising that something actively using regulators (rather
than simply ensuring they're enabled) would be using that function.
Though if you already have ifdefs the ifdef is probably fine.

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