Re: [PATCH] iio: dac: Fix passing uninitialized vref1_uV for no Vref1 case

[Andy Shevchenko <andriy.shevchenko@intel.com>]

On Tue, Apr 14, 2026 at 02:26:45PM +0000, Ariana.Lazar@microchip.com wrote:
> On Tue, 2026-04-14 at 15:48 +0300, Andy Shevchenko wrote:
> > EXTERNAL EMAIL: Do not click links or open attachments unless you
> > know the content is safe

You should get rid of this message. It's incompatible with OSS development
process.

> > On Tue, Apr 14, 2026 at 03:33:38PM +0300, Ariana Lazar wrote:

...

> > > +     vref1_uV = 0;
> > >       if (chip_features->have_ext_vref1) {
> > 
> > I'm wondering what will happen if we do the below unconditionally?
> > 
> > >               ret = devm_regulator_get_enable_read_voltage(dev,
> > > "vref1");
> > 
> > If we have no regulator, we get a dummy one, right? What is the
> > voltage will
> > be? 0?
> > 
> > >               if (ret > 0) {
> > >                       vref1_uV = ret;
> > >                       data->use_vref1 = true;
> > >               } else {
> > > -                     vref1_uV = 0;
> > >                       dev_dbg(dev, "using internal band gap as
> > > voltage reference 1.\n");
> > >                       dev_dbg(dev, "Vref1 is unavailable.\n");
> > >               }
> 
> Thank you for the review.
> 
> This is a safety check to ensure the devicetree matches the available
> hardware. If Vref1 was selected in devicetree but unavailable in
> hardware, the scales MCP47FEB02_SCALE_GAIN_X1 and
> MCP47FEB02_SCALE_GAIN_X2 and also voltage readings would be incorrect
> for the channels that use Vref1.

I didn't get how. What I recommend is to do regulator request unconditionally.

> I did something similiar to what you have suggested in the first patch
> I have submitted for this driver and checking first was recommended.
> 
> https://lore.kernel.org/all/20250927185324.2f9e8061@jic23-huawei/

I briefly read that. The check was there, Jonathan just asked to modify
the check itself IIUC, i.o.w. the semantics of the check was commented
and not the check presence in the first place.

Did I get it wrong? Jonathan, can we get rid of the check and ask for
regulator unconditionally? (Maybe it would be good to print an error
code in the debug message to be sure why it failed to get the regulator
or its voltage.)

-- 
With Best Regards,
Andy Shevchenko