linux-kernel - Re: [PATCH v2 2/9] thermal: core: Add flags to struct thermal

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Message-ID: <CAJZ5v0j6LWGnUfB6fbgHTXFOJ=n857ZSxqbd3u-5_FAVnbhXoQ@mail.gmail.com>
Date: Thu, 22 Feb 2024 17:13:42 +0100
From: "Rafael J. Wysocki" <rafael@...nel.org>
To: Daniel Lezcano <daniel.lezcano@...aro.org>
Cc: "Rafael J. Wysocki" <rjw@...ysocki.net>, Linux PM <linux-pm@...r.kernel.org>, 
	Lukasz Luba <lukasz.luba@....com>, LKML <linux-kernel@...r.kernel.org>, 
	Stanislaw Gruszka <stanislaw.gruszka@...ux.intel.com>, 
	Srinivas Pandruvada <srinivas.pandruvada@...ux.intel.com>, Zhang Rui <rui.zhang@...el.com>, 
	netdev@...r.kernel.org, Ido Schimmel <idosch@...dia.com>, Petr Machata <petrm@...dia.com>, 
	Miri Korenblit <miriam.rachel.korenblit@...el.com>, linux-wireless@...r.kernel.org, 
	Shawn Guo <shawnguo@...nel.org>, Sascha Hauer <s.hauer@...gutronix.de>, 
	Pengutronix Kernel Team <kernel@...gutronix.de>, 
	Manaf Meethalavalappu Pallikunhi <quic_manafm@...cinc.com>
Subject: Re: [PATCH v2 2/9] thermal: core: Add flags to struct thermal_trip

On Thu, Feb 22, 2024 at 4:51 PM Rafael J. Wysocki <rafael@...nel.org> wrote:
>
> On Thu, Feb 22, 2024 at 3:36 PM Daniel Lezcano
> <daniel.lezcano@...aro.org> wrote:
> >
> > On 12/02/2024 19:31, Rafael J. Wysocki wrote:
> > > From: Rafael J. Wysocki <rafael.j.wysocki@...el.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@...el.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?

Even so, the .store() callback will not be set then anyway.

I'll send an update of this patch.