linux-kernel - Re: [PATCH v5 02/30] thermal/sysfs: Do not make get_trip

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Date:   Mon, 26 Sep 2022 21:16:29 +0200
From:   "Rafael J. Wysocki" <rafael@...nel.org>
To:     Daniel Lezcano <daniel.lezcano@...aro.org>
Cc:     "Rafael J. Wysocki" <rafael@...nel.org>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        Linux PM <linux-pm@...r.kernel.org>,
        "Zhang, Rui" <rui.zhang@...el.com>,
        Amit Kucheria <amitk@...nel.org>
Subject: Re: [PATCH v5 02/30] thermal/sysfs: Do not make get_trip_hyst optional

On Mon, Sep 26, 2022 at 4:06 PM Daniel Lezcano
<daniel.lezcano@...aro.org> wrote:
>
> The get_trip_hyst() ops is optional. It results all around the thermal
> framework code a check against the ops pointer and different action
> adding more complexity and making the code less readable and
> understandable.
>
> A zero hysteresis value is perfectly valid, so instead of adding more
> circumvolutions in the code, create unconditionnaly the hysteresis and
> use the thermal_zone_get_trip() function which returns a zero
> hysteresis if the get_trip_hyst() is not defined.
>
> Signed-off-by: Daniel Lezcano <daniel.lezcano@...aro.org>

I would change the subject to something like "thermal/sysfs: Always
expose hysteresis attributes", because that's what the patch does
IIUC.

And in the changelog I would write something like the below:

"Instead of avoiding to expose the hysteresis attributes of a thermal
zone when its get_trip_hyst() operation is not defined, which is
confusing, expose them always and use the default
thermal_zone_get_trip() function returning 0 hysteresis when that
operation is not present.

The hysteresis of 0 is perfectly valid, so this change should not
introduce any backwards compatibility issues."

> ---
>  drivers/thermal/thermal_sysfs.c | 25 +++++++++----------------
>  1 file changed, 9 insertions(+), 16 deletions(-)
>
> diff --git a/drivers/thermal/thermal_sysfs.c b/drivers/thermal/thermal_sysfs.c
> index 75f6b151a58b..18cdd7cd0008 100644
> --- a/drivers/thermal/thermal_sysfs.c
> +++ b/drivers/thermal/thermal_sysfs.c
> @@ -424,23 +424,20 @@ static int create_trip_attrs(struct thermal_zone_device *tz, int mask)
>                 return -ENOMEM;
>         }
>
> -       if (tz->ops->get_trip_hyst) {
> -               tz->trip_hyst_attrs = kcalloc(tz->num_trips,
> -                                             sizeof(*tz->trip_hyst_attrs),
> -                                             GFP_KERNEL);
> -               if (!tz->trip_hyst_attrs) {
> -                       kfree(tz->trip_type_attrs);
> -                       kfree(tz->trip_temp_attrs);
> -                       return -ENOMEM;
> -               }
> +       tz->trip_hyst_attrs = kcalloc(tz->num_trips,
> +                                     sizeof(*tz->trip_hyst_attrs),
> +                                     GFP_KERNEL);
> +       if (!tz->trip_hyst_attrs) {
> +               kfree(tz->trip_type_attrs);
> +               kfree(tz->trip_temp_attrs);
> +               return -ENOMEM;
>         }
>
>         attrs = kcalloc(tz->num_trips * 3 + 1, sizeof(*attrs), GFP_KERNEL);
>         if (!attrs) {
>                 kfree(tz->trip_type_attrs);
>                 kfree(tz->trip_temp_attrs);
> -               if (tz->ops->get_trip_hyst)
> -                       kfree(tz->trip_hyst_attrs);
> +               kfree(tz->trip_hyst_attrs);
>                 return -ENOMEM;
>         }
>
> @@ -473,9 +470,6 @@ static int create_trip_attrs(struct thermal_zone_device *tz, int mask)
>                 }
>                 attrs[indx + tz->num_trips] = &tz->trip_temp_attrs[indx].attr.attr;
>
> -               /* create Optional trip hyst attribute */
> -               if (!tz->ops->get_trip_hyst)
> -                       continue;
>                 snprintf(tz->trip_hyst_attrs[indx].name, THERMAL_NAME_LENGTH,
>                          "trip_point_%d_hyst", indx);
>
> @@ -512,8 +506,7 @@ static void destroy_trip_attrs(struct thermal_zone_device *tz)
>
>         kfree(tz->trip_type_attrs);
>         kfree(tz->trip_temp_attrs);
> -       if (tz->ops->get_trip_hyst)
> -               kfree(tz->trip_hyst_attrs);
> +       kfree(tz->trip_hyst_attrs);
>         kfree(tz->trips_attribute_group.attrs);
>  }
>
> --
> 2.34.1
>