Re: [PATCH v2] hwmon: Add thermal sensor driver for Surface Aggregator Module

[Guenter Roeck]

On 8/7/24 13:11, Maximilian Luz wrote:
> On 8/7/24 9:50 PM, Guenter Roeck wrote:
> > On 8/7/24 12:25, Maximilian Luz wrote:
> > > On 8/7/24 2:32 AM, Guenter Roeck wrote:
> > > > On 8/4/24 16:08, Maximilian Luz wrote:
> > >
> > > [...]
> > >
> > > > > diff --git a/drivers/hwmon/Kconfig b/drivers/hwmon/Kconfig
> > > > > index b60fe2e58ad6..70c6385f0ed6 100644
> > > > > --- a/drivers/hwmon/Kconfig
> > > > > +++ b/drivers/hwmon/Kconfig
> > > > > @@ -2080,6 +2080,16 @@ config SENSORS_SURFACE_FAN
> > > > >         Select M or Y here, if you want to be able to read the fan's speed.
> > > > > +config SENSORS_SURFACE_TEMP
> > > > > +    tristate "Microsoft Surface Thermal Sensor Driver"
> > > > > +    depends on SURFACE_AGGREGATOR
> > > >
> > > > As the kernel test robot points out, this dependency is wrong.
> > > > __ssam_device_driver_register() is only available
> > > > if SURFACE_AGGREGATOR_BUS is enabled.
> > >
> > > Right, I should have spotted this before submission, sorry. This should
> > > be
> > >
> > >    depends on SURFACE_AGGREGATOR
> > >    depends on SURFACE_AGGREGATOR_BUS
> >
> > SURFACE_AGGREGATOR_BUS already depends on SURFACE_AGGREGATOR, so the extra
> > dependency is not needed.
>
> Unfortunately, SURFACE_AGGREGATOR_BUS is a bool and SURFACE_AGGREGATOR
> tri-state, and the inference of whether SURFACE_AGGREGATOR needs to be
> built in or not breaks because of that. Meaning we could have something
> like
>
>      SENSORS_SURFACE_TEMP=y      (tri-state, module)
>      SURFACE_AGGREGATOR_BUS=y    (bool, optional-code-flag)
>      SURFACE_AGGREGATOR=m        (tri-state, module)
>
> because SURFACE_AGGREGATOR_BUS is fine with either m or y. But in
> reality, SENSORS_SURFACE_TEMP=y would require SURFACE_AGGREGATOR=y.

Ah yes, I can see that the double dependency is there everywhere. Normally I'd
have assumed that to be handled with SURFACE_AGGREGATOR_BUS as non-configurable
option and its users selecting it, i.e.,

	depends on SURFACE_AGGREGATOR
	select SURFACE_AGGREGATOR_BUS

but, sure, it is your call to make SURFACE_AGGREGATOR_BUS a configurable
(instead of selectable) option. I don't understand the benefit of being able
to enable SURFACE_AGGREGATOR_BUS without any users, but then maybe I just
don't have sufficient understanding of the context.

Thanks,
Guenter