Re: [PATCH 07/29] mmc: add a function to get a regulator, supplying card's Vdd

[Mark Brown <broonie@opensource.wolfsonmicro.com>]

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On Fri, May 18, 2012 at 11:28:31AM +0200, Guennadi Liakhovetski wrote:

> 1. A regulator that can (in principle) change state, i.e., switch on and 
> off. Such a regulator is good to keep for the runtime to power up and down 
> the card.

> 2. A regulator, that cannot switch, but at least can tell its supplied 
> voltage is used ones to read out supported voltages and released again.

This doesn't make sense, you can only change the voltages if you hold a
reference to the regulator.

> 3. A regulator that can do none of the above is defined as "useless"

> > You may also run into trouble on boards that use the ability to disable
> > unused regulators at the end of boot - they'll power things off even
> > without the ability to change status at runtime.

> Aha, you mean, I shouldn't put() the regulator, even if it cannot change 
> status itself?

Yes, you ought to to be safe and like I say if you want to manage the
voltage then you need to keep a reference to the regulator.

> Can this also happen with a dummy regulator?

Obviously not, though if you've got explicit code in to handle dummy
regulators you're rather missing the point.  Their entire purpose is to
provide a crutch to keep the system going if bits are missing from the
bindings, they're not intended to be used in production.

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