Re: [PATCH v10 1/2] dt-bindings: hwmon: add support for MCP998X

[Victor.Duicu]

Hi Krzysztof,

...
> > > > > > +properties:
> > > > > > +  compatible:
> > > > > > +    enum:
> > > > > > +      - microchip,mcp9933
> > > > > > +      - microchip,mcp9933d
> > > > > > +      - microchip,mcp9982
> > > > > > +      - microchip,mcp9982d
> > > > > > +      - microchip,mcp9983
> > > > > > +      - microchip,mcp9983d
> > > > > > +      - microchip,mcp9984
> > > > > > +      - microchip,mcp9984d
> > > > > > +      - microchip,mcp9985
> > > > > > +      - microchip,mcp9985d
> > > > > > +
> > > > > > +  reg:
> > > > > > +    maxItems: 1
> > > > > > +
> > > > > > +  interrupts:
> > > > > 
> > > > > Your interrupt-names say 1 item is correct, so these are de-
> > > > > synced.
> > > > > They
> > > > > should be always constrained the same way.
> > > > > 
> > > > 
> > > > We want to allow the user to use none, one or both interrupts.
> > > 
> > > Who is the "user" here? IOW, can the *hardware* work correctly
> > > without
> > > the interrupt line connected anywhere?
> > > 
> > 
> > Yes, the hardware can work while the interrupt lines are not
> > connected.
> 
> Almost there...
> 
> > At the moment the driver does not support interrupts.
> 
> 
> ...and ruined it. This does not matter and using it as argument means
> I
> do not believe you actually checked if hardware can work without
> interrupt lines connected. You only checked the driver. Please read
> your
> datasheet carefully.
> 
> Best regards,
> Krzysztof

As described on page 11 of the documentation the alert-therm,
therm-addr and sys-shtdwn pins are of type open-drain.
Most of the devices need a pull-up resistor in order to setup the I2C
address(for parts with name ending in "-A") or to control the
hardware thermal shutdown limit(for chips with "D" in the name).
In all other cases it is recommended to connect a pull-up resistor to
the pin, but it is not mandatory. If the hardware does not use that
signal, the pull-up can be missing.
If the interrupt functionality is used then it's mandatory to use a
pull-up resistor.

In my view the "user" is the person doing the design for a system
which includes the MCP998X chip. Please correct me if I'm wrong,
I am under the impression that the device tree is a hardware descriptor
for the driver to know how the hardware is setup/configured but
should not supersede the datasheet for designing new systems.

Kind regards,
Victor