linux-kernel - Re: [PATCH v4 04/10] thermal: core: Add thermal_zone_update_trip

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Date:   Mon, 7 Aug 2023 18:23:04 +0200
From:   "Rafael J. Wysocki" <rafael@...nel.org>
To:     Daniel Lezcano <daniel.lezcano@...aro.org>
Cc:     "Rafael J. Wysocki" <rafael@...nel.org>,
        "Rafael J. Wysocki" <rjw@...ysocki.net>,
        Linux ACPI <linux-acpi@...r.kernel.org>,
        LKML <linux-kernel@...r.kernel.org>,
        Linux PM <linux-pm@...r.kernel.org>,
        Michal Wilczynski <michal.wilczynski@...el.com>,
        Zhang Rui <rui.zhang@...el.com>,
        Srinivas Pandruvada <srinivas.pandruvada@...ux.intel.com>
Subject: Re: [PATCH v4 04/10] thermal: core: Add thermal_zone_update_trip_temp()
 helper routine

On Mon, Aug 7, 2023 at 6:17 PM Daniel Lezcano <daniel.lezcano@...aro.org> wrote:
>
> On 07/08/2023 17:40, Rafael J. Wysocki wrote:
> > On Mon, Aug 7, 2023 at 1:34 PM Daniel Lezcano <daniel.lezcano@...aro.org> wrote:
> >>
> >> On 04/08/2023 23:05, Rafael J. Wysocki wrote:
> >>> From: Rafael J. Wysocki <rafael.j.wysocki@...el.com>
> >>>
> >>> Introduce a helper routine called thermal_zone_update_trip_temp() that
> >>> can be used to update a trip point's temperature with the help of a
> >>> pointer to local data associated with that trip point provided by
> >>> the thermal driver that created it.
> >>>
> >>> Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@...el.com>
> >>> ---
> >>>
> >>> New patch in v4.
> >>>
> >>> ---
> >>>    drivers/thermal/thermal_trip.c |   37 +++++++++++++++++++++++++++++++++++++
> >>>    include/linux/thermal.h        |    4 ++++
> >>>    2 files changed, 41 insertions(+)
> >>>
> >>> Index: linux-pm/drivers/thermal/thermal_trip.c
> >>> ===================================================================
> >>> --- linux-pm.orig/drivers/thermal/thermal_trip.c
> >>> +++ linux-pm/drivers/thermal/thermal_trip.c
> >>> @@ -180,3 +180,40 @@ int thermal_zone_set_trip(struct thermal
> >>>
> >>>        return 0;
> >>>    }
> >>> +
> >>> +/**
> >>> + * thermal_zone_update_trip_temp - Update the trip point temperature.
> >>> + * @tz: Thermal zone.
> >>> + * @trip_priv: Trip tag.
> >>> + * @temp: New trip temperature.
> >>> + *
> >>> + * This only works for thermal zones using trip tables and its caller must
> >>> + * ensure that the zone lock is held before using it.
> >>> + *
> >>> + * @trip_priv is expected to be the value that has been stored by the driver
> >>> + * in the struct thermal_trip representing the trip point in question, so it
> >>> + * can be matched against the value of the priv field in that structure.
> >>> + *
> >>> + * If @trip_priv does not match any trip point in the trip table of @tz,
> >>> + * nothing happens.
> >>> + */
> >>> +void thermal_zone_update_trip_temp(struct thermal_zone_device *tz,
> >>> +                                void *trip_priv, int temperature)
> >>> +{
> >>> +     int i;
> >>> +
> >>> +     lockdep_assert_held(&tz->lock);
> >>> +
> >>> +     if (!tz->trips || !trip_priv)
> >>> +             return;
> >>> +
> >>> +     for (i = 0; i < tz->num_trips; i++) {
> >>> +             struct thermal_trip *trip = &tz->trips[i];
> >>> +
> >>> +             if (trip->priv == trip_priv) {
> >>> +                     trip->temperature = temperature;
> >>> +                     return;
> >>> +             }
> >>> +     }
> >>> +}
> >>> +EXPORT_SYMBOL_GPL(thermal_zone_update_trip_temp);
> >>
> >> This function would imply the comparator is always trip->priv but if we
> >> want another comparison eg. trip->priv->id, that won't be possible.
> >>
> >> Actually, I think you can reuse an existing function with a simple
> >> change, for_each_thermal_trip() located in thermal_core.h.
> >
> > for_each_thermal_trip() is only defined in tools/lib/thermal/thermal.c
> > AFAICS, but this one could actually work, so I can copy that
> > definition to somewhere else.
> >
> > But I suppose that you mean __for_each_thermal_trip() which won't
> > work, because it makes a copy of the trip and passes that to the
> > callback, but the callback would need to update the temperature of the
> > original trip.
> >
> > It would work if it passed the original trip to the caller, so I can
> > add something like that.
>
> As there is no user of this function yet, I think you can change that to
> use the trip array instead of the __thermal_zone_get_trip(). This one
> was used to have a compatibility with thermal zones using get_trip_* ops
> but that is not really needed and with your series only one driver will
> remain before dropping these ops.

Sounds good.

> >> The changes would be renaming it without the '__' prefix and moving it
> >> in include/linux/thermal.h.
> >>
> >> Then the comparison function and the temperature change can be an ACPI
> >> driver specific callback passed as parameter to for_each_thermal_zone
> >
> > I guess you mean for_each_thermal_trip().
>
> Yes, __for_each_thermal_trip()

OK