> >> + }
> >> +
> >> + return -EINVAL;
> >> +};
> >> +
> >> +static const struct iio_backend_ops sd_backend_ops = {
> >> + .enable = sd_backend_enable,
> >> + .disable = sd_backend_disable,
> >> + .read_raw = sd_backend_read,
> >> +};
> >> +
> >> +static int iio_sd_backend_probe(struct platform_device *pdev)
> >> +{
> >> + struct device *dev = &pdev->dev;
> >> + struct regulator *vref;
> >> + struct iio_sd_backend_priv *priv;
> >> + int ret;
> >> +
> >> + priv = devm_kzalloc(dev, sizeof(*priv), GFP_KERNEL);
> >> + if (!priv)
> >> + return -ENOMEM;
> >> +
> >> + vref = devm_regulator_get_optional(dev, "vref");
> >
> > New devm_regulator_get_enable_read_voltage() slightly simplifies this
> > and means you don't need to keep vref around.
> >
> >> + if (IS_ERR(vref)) {
> >> + if (PTR_ERR(vref) != -ENODEV)
> >> + return dev_err_probe(dev, PTR_ERR(vref), "Failed to get vref\n");
> >> + } else {
> >> + ret = regulator_get_voltage(vref);
> > You haven't turned it on so it's not guaranteed to give you a useful
> > answer.
> >
>
> My understanding is that regulator_get_voltage() always returns the
> regulator voltage, whatever the regulator state, as documented in the
> API description:
> "* NOTE: If the regulator is disabled it will return the voltage value.
> * This function should not be used to determine regulator state."
>
> So, my logic was to enable the regulator only when requested, through
> enable/disable callbacks to manage power.
>
> Please, let me know if I missed something here.
Ah ok. I had a vague and it seems incorrect recollection that you had
to turn the regs on to get voltage in some cases. Ah well. Clearly not :)
What you have is fine. Add a comment though just so no one replaces
this code with the helper.
Jonathan
