Re: [PATCH 1/1 v3] pwm_bl: Add support for backlight enable regulator

[Alex Courbot]

On 03/06/2013 01:20 PM, Stephen Warren wrote:
> On 03/05/2013 07:18 PM, Alex Courbot wrote:
> > On 03/06/2013 08:51 AM, Andrew Chew wrote:
> > > The backlight enable regulator is specified in the device tree node for
> > > backlight.
>
> > > diff --git a/include/linux/pwm_backlight.h
>
> > >    struct platform_pwm_backlight_data {
> > >        int pwm_id;
> > > +    struct regulator *en_supply;
> >
> > You should not have this here. Platform data is supposed to provide the
> > necessary information for the driver to resolve the resource - not the
> > resource itself.
> ...
> > There is one catch though: in case you don't want to use a regulator,
> > and thus have none defined, regulator_get() will return -EPROBE_DEFER,
> > so you cannot distinguish between "no regulator needed" and "supplier
> > not ready yet" and your driver will always *require* a regulator. So at
> > the end of the day you might still need a "use_enable_regulator" in the
> > platform data to explicitly ask for probe() to look for it. This
> > variable would also be set by parse_dt() if the "enable-supply" property
> > exists.
>
> A driver that requires a regulator always requires that regulator. If a
> particular board doesn't have SW control over the power source, you're
> supposed to provide a dummy (fixed) regulator so that the driver doesn't
> care about the difference.

That's good to know, thanks. So does this mean that Andrew should make 
the enable regulator mandatory and update current users to provide a 
dummy one?

Alex.

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