Re: [PATCH v5 1/3] thermal/acpi: Add ACPI trip point routines

[Daniel Lezcano]

On 20/01/2023 19:15, Rafael J. Wysocki wrote:
> On Fri, Jan 20, 2023 at 7:08 PM Daniel Lezcano
> <daniel.lezcano@xxxxxxxxxx> wrote:
> > Hi Rafael,
> >
> >
> > On 19/01/2023 14:15, Rafael J. Wysocki wrote:
> >
> > [ ... ]
> >
> > > > +static int thermal_acpi_get_temperature_object(struct acpi_device *adev,
> > > > +                                              char *object, int *temperature)
> > >
> > > So this would become thermal_acpi_get_temp_object(). or even
> > > thermal_acpi_get_temp() because it really returns the temperature
> > > value.
> > >
> > > I also don't particularly like returning values via pointers, which is
> > > entirely avoidable here, because the temperature value obtained from
> > > the ACPI control methods must be a positive number.
> > >
> > > So I would make it
> > >
> > > static int thermal_acpi_get_temp(struct acpi_device *adev, char *object_name)
> > > {
> >
> > We are converting decikelvin -> millicelsius. Even it is very unlikely,
> > the result could be less than zero (eg. -1°C). We won't be able to
> > differentiate -ENODATA with a negative value, no ?
> >
> > In the future, it is possible we will have to deal with cold trip points
> > in order to warm a board. May be we should don't care for now ?
>
> My point is that the ACPI specification mandates that the return
> values be in deciK and so always non-negative.

I understand that but the code does:

static int thermal_acpi_get_temp(struct acpi_device *adev, char 
*object_name)
{
	...

	return deci_kelvin_to_millicelsius(temp);
}

All the callers do:

...

        ret = thermal_acpi_get_temp(adev, name);
        if (ret < 0)
		return ret;
	/* This could be an error
	 * or negative millicelsius temperature
	 */

	/* here we already have millicelsius */
        trip->temperature = ret;
...

So I guess we want to do:

...

        ret = thermal_acpi_get_temp(adev, name);
        if (ret < 0)
		return ret;

	/* we convert here instead in thermal_acpi_get_temp() */
        trip->temperature = deci_kelvin_to_millicelsius(ret);
...

Sounds good ?


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