Re: [PATCH 3/4] mfd: mt6397-core: add mt6323 AUXADC support

[Roman Vivchar]

Hi Lee,

On Thursday, June 11th, 2026 at 7:37 PM, Lee Jones <lee@xxxxxxxxxx> wrote:
> Interesting.  Has this been considered?
> 
> /* Sashiko Automation: Issues Found (1 Findings) */
> 
> On Tue, 02 Jun 2026, Roman Vivchar via B4 Relay wrote:
> 
> > From: Roman Vivchar <rva333@xxxxxxxxxxxxxx>
> >
> > The mt6323 PMIC includes an AUXADC. Register the AUXADC in the mt6323
> > devices array to allow the corresponding driver to probe using compatible
> > string.
> >
> > Tested-by: Ben Grisdale <bengris32@xxxxxxxxxxxxx> # Amazon Echo Dot (2nd Generation)
> > Signed-off-by: Roman Vivchar <rva333@xxxxxxxxxxxxxx>
> > ---
> >  drivers/mfd/mt6397-core.c | 3 +++
> >  1 file changed, 3 insertions(+)
> >
> > diff --git a/drivers/mfd/mt6397-core.c b/drivers/mfd/mt6397-core.c
> > index 3e58d0764c7e..013b0857fb54 100644
> > --- a/drivers/mfd/mt6397-core.c
> > +++ b/drivers/mfd/mt6397-core.c
> > @@ -125,6 +125,9 @@ static const struct resource mt6323_pwrc_resources[] = {
> >
> >  static const struct mfd_cell mt6323_devs[] = {
> >  	{
> > +		.name = "mt6323-auxadc",
> > +		.of_compatible = "mediatek,mt6323-auxadc",
> 
> [Severity: High]
> Does adding this compatible string expose an unhandled edge case in the
> auxadc driver?
> 
> If this device is instantiated directly from a Device Tree without an MFD
> parent (e.g., at the DT root), dev->parent could be the platform bus
> (which has a NULL parent) or NULL itself.
> 
> Looking at mt6323_auxadc_probe() in drivers/iio/adc/mt6323-auxadc.c:
> 
>     regmap = dev_get_regmap(dev->parent->parent, NULL);
> 
> Could blindly dereferencing dev->parent->parent here, or passing a NULL
> device to dev_get_regmap() (which calls devres_find()), result in a
> kernel oops if probed as a root node?

This is intended behavior, ADC always should be probed as a child of
the mt6323 MFD because it doesn't have own MMIO space. Otherwise the
devicetree is malformed. Recent mt6359 ADC driver has same thing with
dev->parent->parent regmap.

Best regards,
Roman