Re: [PATCH v2 2/9] thermal: core: Add flags to struct thermal_trip

["Rafael J. Wysocki" <rafael@kernel.org>]

On Thu, Feb 22, 2024 at 3:36 PM Daniel Lezcano
<daniel.lezcano@linaro.org> wrote:
>
> On 12/02/2024 19:31, Rafael J. Wysocki wrote:
> > From: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
> >
> > In order to allow thermal zone creators to specify the writability of
> > trip point temperature and hysteresis on a per-trip basis, add a flags
> > field to struct thermal_trip and define flags to represent the desired
> > trip properties.
> >
> > Also make thermal_zone_device_register_with_trips() set the
> > THERMAL_TRIP_FLAG_RW_TEMP flag for all trips covered by the writable
> > trips mask passed to it and modify the thermal sysfs code to look at
> > the trip flags instead of using the writable trips mask directly or
> > checking the presence of the .set_trip_hyst() zone callback.
> >
> > Additionally, make trip_point_temp_store() and trip_point_hyst_store()
> > fail with an error code if the trip passed to one of them has
> > THERMAL_TRIP_FLAG_RW_TEMP or THERMAL_TRIP_FLAG_RW_HYST,
> > respectively, clear in its flags.
> >
> > No intentional functional impact.
> >
> > Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
> > ---
> >
> > v1 -> v2:
> >     * Rename trip flags (Stanislaw).
> >
> > ---
> >   drivers/thermal/thermal_core.c  |   12 +++++++++++-
> >   drivers/thermal/thermal_core.h  |    2 +-
> >   drivers/thermal/thermal_sysfs.c |   28 +++++++++++++++++++---------
> >   include/linux/thermal.h         |    7 +++++++
> >   4 files changed, 38 insertions(+), 11 deletions(-)
> >
> > Index: linux-pm/include/linux/thermal.h
> > ===================================================================
> > --- linux-pm.orig/include/linux/thermal.h
> > +++ linux-pm/include/linux/thermal.h
> > @@ -64,15 +64,23 @@ enum thermal_notify_event {
> >    * @threshold: trip crossing notification threshold miliCelsius
> >    * @type: trip point type
> >    * @priv: pointer to driver data associated with this trip
> > + * @flags: flags representing binary properties of the trip
> >    */
> >   struct thermal_trip {
> >       int temperature;
> >       int hysteresis;
> >       int threshold;
> >       enum thermal_trip_type type;
> > +     u8 flags;
> >       void *priv;
> >   };
> >
> > +#define THERMAL_TRIP_FLAG_RW_TEMP    BIT(0)
> > +#define THERMAL_TRIP_FLAG_RW_HYST    BIT(1)
> > +
> > +#define THERMAL_TRIP_FLAG_MASK_RW    (THERMAL_TRIP_FLAG_RW_TEMP | \
> > +                                      THERMAL_TRIP_FLAG_RW_HYST)
>
> What about THERMAL_TRIP_FLAG_RW instead ?

Fine with me.

> >   struct thermal_zone_device_ops {
> >       int (*bind) (struct thermal_zone_device *,
> >                    struct thermal_cooling_device *);
> > Index: linux-pm/drivers/thermal/thermal_core.c
> > ===================================================================
> > --- linux-pm.orig/drivers/thermal/thermal_core.c
> > +++ linux-pm/drivers/thermal/thermal_core.c
> > @@ -1356,13 +1356,23 @@ thermal_zone_device_register_with_trips(
> >       tz->devdata = devdata;
> >       tz->trips = trips;
> >       tz->num_trips = num_trips;
> > +     if (num_trips > 0) {
>
> Is this check really necessary?

No, it isn't.

> for_each_trip() should exit immediately if there is no trip points.

Right.

> > +             struct thermal_trip *trip;
> > +
> > +             for_each_trip(tz, trip) {
> > +                     if (mask & 1)
> > +                             trip->flags |= THERMAL_TRIP_FLAG_RW_TEMP;
> > +
> > +                     mask >>= 1;
> > +             }
> > +     }
> >
> >       thermal_set_delay_jiffies(&tz->passive_delay_jiffies, passive_delay);
> >       thermal_set_delay_jiffies(&tz->polling_delay_jiffies, polling_delay);
> >
> >       /* sys I/F */
> >       /* Add nodes that are always present via .groups */
> > -     result = thermal_zone_create_device_groups(tz, mask);
> > +     result = thermal_zone_create_device_groups(tz);
> >       if (result)
> >               goto remove_id;
> >
> > Index: linux-pm/drivers/thermal/thermal_core.h
> > ===================================================================
> > --- linux-pm.orig/drivers/thermal/thermal_core.h
> > +++ linux-pm/drivers/thermal/thermal_core.h
> > @@ -131,7 +131,7 @@ void thermal_zone_trip_updated(struct th
> >   int __thermal_zone_get_temp(struct thermal_zone_device *tz, int *temp);
> >
> >   /* sysfs I/F */
> > -int thermal_zone_create_device_groups(struct thermal_zone_device *, int);
> > +int thermal_zone_create_device_groups(struct thermal_zone_device *tz);
> >   void thermal_zone_destroy_device_groups(struct thermal_zone_device *);
> >   void thermal_cooling_device_setup_sysfs(struct thermal_cooling_device *);
> >   void thermal_cooling_device_destroy_sysfs(struct thermal_cooling_device *cdev);
> > Index: linux-pm/drivers/thermal/thermal_sysfs.c
> > ===================================================================
> > --- linux-pm.orig/drivers/thermal/thermal_sysfs.c
> > +++ linux-pm/drivers/thermal/thermal_sysfs.c
> > @@ -122,6 +122,11 @@ trip_point_temp_store(struct device *dev
> >
> >       trip = &tz->trips[trip_id];
> >
> > +     if (!(trip->flags & THERMAL_TRIP_FLAG_RW_TEMP)) {
> > +             ret = -EPERM;
> > +             goto unlock;
> > +     }
>
> Does it really happen?
>
> If the sysfs file is created with the right permission regarding the
> trip->flags then this condition can never be true.

But the permissions can be changed after the file has been created, can't they?