linux-kernel - Re: [PATCH] regulator: Provide optional dummy regulator for consumers

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Date:	Sat, 13 Feb 2010 01:01:07 +0200
From:	Grazvydas Ignotas <notasas@...il.com>
To:	Mark Brown <broonie@...nsource.wolfsonmicro.com>
Cc:	Liam Girdwood <lrg@...mlogic.co.uk>,
	Mike Rapoport <mike@...pulab.co.il>,
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH] regulator: Provide optional dummy regulator for consumers

On Fri, Feb 12, 2010 at 12:18 PM, Mark Brown
<broonie@...nsource.wolfsonmicro.com> wrote:
> In order to ease transitions with drivers are boards start using regulators
> provide an option to cause all regulator_get() calls to succeed, with a
> dummy always on regulator being supplied where one has not been configured.
> A warning is printed whenever the dummy regulator is used to aid system
> development.
>
> This regulator does not implement any regulator operations but will allow
> simple consumers which only do enable() and disable() calls to run. It
> is kept separate from the fixed voltage regulator to avoid Kconfig
> confusion on the part of users when it is extended to allow boards to
> explicitly use the dummy regulator to simplify cases where the majority
> of supplies are from fixed regulators without software control.
>
> This option is currently only effective for systems which do not specify
> full constriants. If required an override could also be provided to allow
> these systems to use the dummy regulator, though it is likely that
> unconfigured supplies on such systems will lead to error due to
> regulators being powered down more aggressively when not in use.
>
> Signed-off-by: Mark Brown <broonie@...nsource.wolfsonmicro.com>
> ---
>

hm, tried intentionally nuking regulator setup on my board to test
dummy and drivers started failing on regulator_enable() with -1
(EPERM?). Looks like dummy doesn't have constraints defined, so not
much use of this if _enable() is failing anyway.

BTW, drivers/mmc/host/omap_hsmmc.c has quite a lot of logic related to
vcc_aux being available or not (vcc_aux is typically used to power
some MMC pins and is unused on devices with SD cards, like pandora). I
wonder if it may cause some functionality change there.
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