Re: [RFC PATCH] thermal/core: Fix trip point crossing events ordering

[Daniel Lezcano]

On 06/03/2024 16:41, Rafael J. Wysocki wrote:
> On Wed, Mar 6, 2024 at 2:16 PM Daniel Lezcano <daniel.lezcano@xxxxxxxxxx> wrote:
> > On 06/03/2024 13:53, Rafael J. Wysocki wrote:
> > > On Wed, Mar 6, 2024 at 1:43 PM Daniel Lezcano <daniel.lezcano@xxxxxxxxxx> wrote:
> > > > On 06/03/2024 13:02, Rafael J. Wysocki wrote:
> > > >
> > > > [ ... ]
> > > >
> > > > > > +#define for_each_trip_reverse(__tz, __trip)    \
> > > > > > +       for (__trip = &__tz->trips[__tz->num_trips - 1]; __trip >= __tz->trips ; __trip--)
> > > > > > +
> > > > > >     void __thermal_zone_set_trips(struct thermal_zone_device *tz);
> > > > > >     int thermal_zone_trip_id(const struct thermal_zone_device *tz,
> > > > > >                             const struct thermal_trip *trip);
> > > > > > --
> > > > >
> > > > > Generally speaking, this is a matter of getting alignment on the
> > > > > expectations between the kernel and user space.
> > > > >
> > > > > It looks like user space expects to get the notifications in the order
> > > > > of either growing or falling temperatures, depending on the direction
> > > > > of the temperature change.  Ordering the trips in the kernel is not
> > > > > practical, but the notifications can be ordered in principle.  Is this
> > > > > what you'd like to do?
> > > >
> > > > Yes
> > > >
> > > > > Or can user space be bothered with recognizing that it may get the
> > > > > notifications for different trips out of order?
> > > >
> > > > IMO it is a bad information if the trip points events are coming
> > > > unordered. The temperature signal is a time related measurements, the
> > > > userspace should receive thermal information from this signal in the
> > > > right order. It sounds strange to track the temperature signal in the
> > > > kernel, then scramble the information, pass it to the userspace and
> > > > except it to apply some kind of logic to unscramble it.
> > >
> > > So the notifications can be ordered before sending them out, as long
> > > as they are produced by a single __thermal_zone_device_update() call.
> > >
> > > I guess you also would like the thermal_debug_tz_trip_up/down() calls
> > > to be ordered, wouldn't you?
> >
> > Right
>
> I have an idea how to do this, but it is based on a couple of patches
> that I've been working on in the meantime.
>
> Let me post these patches first and then I'll send a prototype patch
> addressing this on top of them.

That is awesome, thanks !

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