On 2 September 2016 at 15:40, Lars-Peter Clausen <lars@xxxxxxxxxx> wrote:
> Hi,
>
> Thanks for the patch.
>
> On 09/02/2016 03:27 PM, Crt Mori wrote:
>> This patch is inspired by a comment of Jonathan Cameron on patch of
>> Linus Walleij commit aeb55fff3891834e07a3144159a7298a19696af8 ("iio: st_sensors: fetch and enable regulators unconditionally").
>>
>> The explanation for this change is same as in that patch:
>> "Supplies are *not* optional (optional means that the supply is
>> optional in the electrical sense, not the software sense) so we need to
>> get the and enable them at all times.
>
> Some supplies are optional. I.e. the part is able to operate (potentially
> with limited functionality) even if the optional external supply has not
> been connected to the pin.
>
> E.g. many converters have a built-in voltage reference but are able to
> optionally accept an external reference. The driver needs to know if the
> external reference is not connected or not to be able to allow or disallow
> applications to switch the part into external reference mode. This is the
> case for the ad7266 and ad5761 drivers and using regulator_get_optional() is
> correct here.
>
> Same seems to be true for the ads8688 and the fsl-imx-gcq, judging by how
> their code is structured.
>
> - Lars
OK, so the voltage reference part can have optional regulator, but if
it is supply voltage then it cannot.
What about the IS_ERR_OR_NULL() check? Is that suitable for the
optional regulators as well?
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