Re: [PATCH v3 1/2] hwmon: (lm90) Add power control

[Guenter Roeck]

On 09/09/2013 08:40 PM, Stephen Warren wrote:
> On 09/09/2013 09:36 PM, Guenter Roeck wrote:
> > On 09/09/2013 08:22 PM, Wei Ni wrote:
> > > On 09/09/2013 11:50 PM, Guenter Roeck wrote:
> > > > On Mon, Sep 09, 2013 at 02:50:22PM +0100, Mark Brown wrote:
> > > > > On Mon, Sep 09, 2013 at 04:34:43AM -0700, Guenter Roeck wrote:
> > > > > > On 09/09/2013 04:12 AM, Mark Brown wrote:
> > > > > > > On Mon, Sep 09, 2013 at 06:29:11PM +0800, Wei Ni wrote:
> > > > >
> > > > > > > This doesn't look good, it is going to ignore actual errors - I
> > > > > > > *really*
> > > > > > > doubt that vcc is optional, it looks like it's the main power
> > > > > > > supply for
> > > > > > > the device.  You should use normal regulator_get(), _optional() is
> > > > > > > for
> > > > > > > supplies which could physically not be provided in a system (eg,
> > > > > > > if the
> > > > > > > device can generate them internally if required).
> > > > >
> > > > > > Then he'll have to make sure that all devicetree files in the system
> > > > > > contain references to this regulator.
> > > > >
> > > > > Or get the patches applied on top of the code that'll be going in this
> > > > > cycle implementing get_optional() properly - when that's done the
> > > > > default will be to provide a dummy supply for regulator_get().  If you
> > > > > ack the patch I'd be happy to carry it.
> > > > Jean will have to ack it.
> > > I think it's better to use get_optional(), and ignore the errors except
> > > -EPROBE_DEFER. Because many platform may always power on this device,
> > > and will not provide regulator for it, so if we get errors from
> > > regulator subsystem and return it directly, then the probe() can't be
> > > implemented, this driver can't work properly, even though it can work
> > > without regulator support.
> > > Mark, do you mean you have patches for regulator_get_optional() and
> > > regulator_get()?
> >
> > My understanding is that by adding regulator support you essentially
> > committed to adding regulators (if necessary dummy ones) for this driver
> > to all those platforms. This is quite similar to other drivers in the
> > same situation. Once you start along that route, you'll have to go it
> > all the way.
>
> By using regulator_get_optional(), the regulator should be optional,
> hence you only have to add it to platforms that need it.

Earlier comments suggest that this is not the intended use case for
regulator_get_optional().

Guenter

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