Date: Mon, 17 Jun 2024 20:55:06 +0200
From: "Rafael J. Wysocki" <rafael@...nel.org>
To: Niklas Söderlund <niklas.soderlund+renesas@...natech.se>
Cc: "Rafael J. Wysocki" <rjw@...ysocki.net>, Linux PM <linux-pm@...r.kernel.org>, 
	LKML <linux-kernel@...r.kernel.org>, "Rafael J. Wysocki" <rafael@...nel.org>, 
	Lukasz Luba <lukasz.luba@....com>, Daniel Lezcano <daniel.lezcano@...aro.org>, 
	Geert Uytterhoeven <geert@...ux-m68k.org>
Subject: Re: [PATCH v1 13/14] thermal: trip: Replace thermal_zone_get_num_trips()

Hi Niklas,

On Mon, Jun 17, 2024 at 8:39 PM Niklas Söderlund
<niklas.soderlund+renesas@...natech.se> wrote:
>
> Hi Rafael,
>
> Thanks for your patch.
>
> On 2024-06-17 20:11:30 +0200, Rafael J. Wysocki wrote:
> > From: Rafael J. Wysocki <rafael.j.wysocki@...el.com>
> >
> > The only existing caller of thermal_zone_get_num_trips(), which is
> > rcar_gen3_thermal_probe(), uses this function to check whether or
> > not the number of trips in the given thermal zone is nonzero.
> >
> > Because it really only needs to know whether or not the given
> > thermal zone is tripless, replace thermal_zone_get_num_trips() with
> > thermal_zone_is_tripless() that can tell rcar_gen3_thermal_probe()
> > exactly what it needs to know and make it call that function.
> >
> > No intentional functional impact.
> >
> > Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@...el.com>
> > ---
> >  drivers/thermal/renesas/rcar_gen3_thermal.c |    3 +--
> >  drivers/thermal/thermal_trip.c              |    6 +++---
> >  include/linux/thermal.h                     |    2 +-
> >  3 files changed, 5 insertions(+), 6 deletions(-)
> >
> > Index: linux-pm/drivers/thermal/renesas/rcar_gen3_thermal.c
> > ===================================================================
> > --- linux-pm.orig/drivers/thermal/renesas/rcar_gen3_thermal.c
> > +++ linux-pm/drivers/thermal/renesas/rcar_gen3_thermal.c
> > @@ -563,8 +563,7 @@ static int rcar_gen3_thermal_probe(struc
> >               if (ret)
> >                       goto error_unregister;
> >
> > -             ret = thermal_zone_get_num_trips(tsc->zone);
> > -             if (ret < 0)
> > +             if (thermal_zone_is_tripless(tsc->zone))
>
> There are two issues with this change.
>
> 1. The original code only jumped to error_unregister if there where a
>    negative number of trip points, presumably to allow for an error to
>    be returned when reading the number of trip points.
>
>    If an negative error was found it was stored in ret, and this was
>    then returned from the probe function after jumping to
>    error_unregister. This change jumps to the error out path, but do not
>    fail probe.
>
>    However it is valid to complete probe without any trip points found.
>    So failing probe on thermal_zone_is_tripless() is not desired.
>
> 2. The value returned from thermal_zone_get_num_trips() and stored in
>    ret is used in a dev_info() below, logging how many trip points (if
>    any) where found.
>
>    With this change that is no longer true and it will always log 0 trip
>    points found.

You are right, I've overlooked the above.

> As there is no long (if there ever where) a reason to check for errors
> when reading the number of trip points, and no real use to log the
> number of trip points found maybe a modified patch can do what you want
> (not tested).
>
> - ret = thermal_zone_get_num_trips(tsc->zone);
> - if (ret < 0)
> -    goto error_unregister;
> -
> - dev_info(dev, "Sensor %u: Loaded %d trip points\n", i, ret);
> + dev_info(dev, "Sensor %u: Loaded %s trip points\n", i,
> +       thermal_zone_is_tripless(tsc->zone) ? "with" : "without");
>
> What do you think?

I would rather first update the driver to stop failing when the zone
is tripless, in a separate patch.

Fortunately, the $subject patch is not really needed in the series, so
please regard it as withdrawn for now and we can get back to this
later.

Thanks!

>
> >                       goto error_unregister;
> >
> >               dev_info(dev, "Sensor %u: Loaded %d trip points\n", i, ret);
> > Index: linux-pm/drivers/thermal/thermal_trip.c
> > ===================================================================
> > --- linux-pm.orig/drivers/thermal/thermal_trip.c
> > +++ linux-pm/drivers/thermal/thermal_trip.c
> > @@ -55,11 +55,11 @@ int thermal_zone_for_each_trip(struct th
> >  }
> >  EXPORT_SYMBOL_GPL(thermal_zone_for_each_trip);
> >
> > -int thermal_zone_get_num_trips(struct thermal_zone_device *tz)
> > +bool thermal_zone_is_tripless(struct thermal_zone_device *tz)
> >  {
> > -     return tz->num_trips;
> > +     return tz->num_trips == 0;
> >  }
> > -EXPORT_SYMBOL_GPL(thermal_zone_get_num_trips);
> > +EXPORT_SYMBOL_GPL(thermal_zone_is_tripless);
> >
> >  /**
> >   * thermal_zone_set_trips - Computes the next trip points for the driver
> > Index: linux-pm/include/linux/thermal.h
> > ===================================================================
> > --- linux-pm.orig/include/linux/thermal.h
> > +++ linux-pm/include/linux/thermal.h
> > @@ -210,7 +210,7 @@ int for_each_thermal_trip(struct thermal
> >  int thermal_zone_for_each_trip(struct thermal_zone_device *tz,
> >                              int (*cb)(struct thermal_trip *, void *),
> >                              void *data);
> > -int thermal_zone_get_num_trips(struct thermal_zone_device *tz);
> > +bool thermal_zone_is_tripless(struct thermal_zone_device *tz);
> >  void thermal_zone_set_trip_temp(struct thermal_zone_device *tz,
> >                               struct thermal_trip *trip, int temp);
> >
> >
> >
> >
>
> --

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