linux-kernel - Re: [PATCH 4/5] thermal/core: Enforce paired .bind/.unbind callbacks

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Date:   Fri, 24 Mar 2023 14:25:35 +0100
From:   "Rafael J. Wysocki" <rafael@...nel.org>
To:     Zhang Rui <rui.zhang@...el.com>
Cc:     linux-pm@...r.kernel.org, rafael.j.wysocki@...el.com,
        daniel.lezcano@...aro.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH 4/5] thermal/core: Enforce paired .bind/.unbind callbacks

On Fri, Mar 24, 2023 at 2:24 PM Rafael J. Wysocki <rafael@...nel.org> wrote:
>
> On Fri, Mar 24, 2023 at 8:08 AM Zhang Rui <rui.zhang@...el.com> wrote:
> >
> > The .bind/.unbind callbacks are designed to allow the thermal zone
> > device to bind to/unbind from a matched cooling device, with thermal
> > instances created/deleted.
> >
> > In this sense, .bind/.unbind callbacks must exist in pairs.
> >
> > Signed-off-by: Zhang Rui <rui.zhang@...el.com>
> > ---
> >  drivers/thermal/thermal_core.c | 5 +++++
> >  1 file changed, 5 insertions(+)
> >
> > diff --git a/drivers/thermal/thermal_core.c b/drivers/thermal/thermal_core.c
> > index 5225d65fb0e0..9c447f22cb39 100644
> > --- a/drivers/thermal/thermal_core.c
> > +++ b/drivers/thermal/thermal_core.c
> > @@ -1258,6 +1258,11 @@ thermal_zone_device_register_with_trips(const char *type, struct thermal_trip *t
> >         if (num_trips > 0 && (!ops->get_trip_type || !ops->get_trip_temp) && !trips)
> >                 return ERR_PTR(-EINVAL);
> >
> > +       if ((ops->bind && !ops->unbind) || (!ops->bind && ops->unbind)) {
>
> This can be written as
>
>         if (!!ops->bind != !!ops->unbind) {

Or even

        if (!ops->bind != !ops->unbind) {

for that matter.

>
> > +               pr_err("Thermal zone device .bind/.unbind not paired\n");
>
> And surely none of the existing drivers do that?  Because it would be
> a functional regression if they did.
>
> > +               return ERR_PTR(-EINVAL);
> > +       }
> > +
> >         if (!thermal_class)
> >                 return ERR_PTR(-ENODEV);
> >
> > --