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

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

On Mon, Jun 15, 2026 at 11:10:20PM +0000, Roman Vivchar wrote:
> On Thursday, June 11th, 2026 at 7:37 PM, Lee Jones <lee@kernel.org> wrote:
> > On Tue, 02 Jun 2026, Roman Vivchar via B4 Relay wrote:

...

> > > +		.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.

I think Sashiko is overprotective here, but if changing, the whole lot of MFD
drivers should be changed (like Rafael recently has done for driver_override
issue in ACPI related drivers).

-- 
With Best Regards,
Andy Shevchenko