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

[Guenter Roeck <linux@roeck-us.net>]

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