Re: [PATCH 2/2] hwmon: (pmbus) Add driver for Analog Devices MAX20912 and MAX20916

[Guenter Roeck <linux@roeck-us.net>]

On Thu, Jul 09, 2026 at 09:54:22AM +0100, Nuno Sá wrote:
> > 
> > Based on the MAX20912/16 specs on my hand, these chips do not support
> > PMBUS_PHASE (0x04). Furthermore, the spec only indicates support for VID mode
> > and does not provide m/b/r. Therefore, some of the features you mentioned might
> > be specific to the MAX20826 series.
> 
> I see, phases are not supported using standard PMBUS.
> 

As mentioned in my other e-mail, it can still be supported by the driver.
That is what the chip drivers are for, after all.

> > 
> > Regarding enabling VOUT via GPIO, our platform handles this via the CPLD as
> > part of the hardware power sequencing. Managing this pin through the driver is
> > not a requirement for our system.
> 
> But we cannot assume all systems will behave like the above. But now i
> do wonder about controlling the GPIOs in the driver. In your system you
> clearly did not need to do it. In mine (testing with a rpi) I had to
> use a GPIO (well I could have used hogs or pinctrl). But if you control the pin
> you do gain the ability to turn off the regulator. If you don't it's always on
> (which might be indeed the bulk of the real usecases for these systems).
> 
Agreed. I don't really like it, but if the chip and some specific hardware
mandate it, it should be supported. However, that code also needs to be
tested - an untested implementation would be worse than no implementation.

Note to anyone from Analog listening: It is really unfortunate that I,
as subsystem maintainer, do not have access to datasheets. That means I have
to rely on assumptions and can not really provide actionable feedback other
than guesswork based on the PMBus standard. That feedback may and likely
will miss essential details.

Thanks,
Guenter