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 <92311e54-8ae8-d9a5-2597-f2b9b447cfb5@linaro.org>
In-Reply-To: <92311e54-8ae8-d9a5-2597-f2b9b447cfb5@linaro.org>
From:   Wei Wang <wvw@google.com>
Date:   Mon, 9 Dec 2019 13:13:33 -0800
Message-ID: <CAGXk5yrvfJW62NHRHRJ4KtQEp5qxfr1V=R37kHMnkV9xgbEU3g@mail.gmail.com>
Subject: Re: [PATCH v3 1/3] thermal: prevent cooling device with no type to be registered
To:     Daniel Lezcano <daniel.lezcano@linaro.org>
Cc:     Wei Wang <wei.vince.wang@gmail.com>,
        Zhang Rui <rui.zhang@intel.com>,
        Eduardo Valentin <edubezval@gmail.com>,
        Amit Kucheria <amit.kucheria@verdurent.com>,
        Linux PM list <linux-pm@vger.kernel.org>,
        LKML <linux-kernel@vger.kernel.org>
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On Mon, Dec 9, 2019 at 11:36 AM Daniel Lezcano
<daniel.lezcano@linaro.org> wrote:
>
> On 05/12/2019 08:19, Wei Wang wrote:
> > commit 54fa38cc2eda ("thermal: core: prevent zones with no types to be
> > registered") added logic to prevent thermal zone with empty type to be
> > registered. Similarly, there are APIs that rely on cdev->type.
> > This patch prevents cooling device without valid type to be registered.
> >
> > Signed-off-by: Wei Wang <wvw@google.com>
> > ---
> >  drivers/thermal/thermal_core.c | 16 +++++++++++++---
> >  1 file changed, 13 insertions(+), 3 deletions(-)
> >
> > diff --git a/drivers/thermal/thermal_core.c b/drivers/thermal/thermal_c=
ore.c
> > index d4481cc8958f..974e2d91c30b 100644
> > --- a/drivers/thermal/thermal_core.c
> > +++ b/drivers/thermal/thermal_core.c
> > @@ -954,12 +954,22 @@ __thermal_cooling_device_register(struct device_n=
ode *np,
> >       struct thermal_zone_device *pos =3D NULL;
> >       int result;
> >
> > -     if (type && strlen(type) >=3D THERMAL_NAME_LENGTH)
> > +     if (!type || !type[0]) {
>
> Why not use strlen(type) =3D=3D 0 ?

Checking empty is faster than getting length and this is already a
pattern used in this file:
https://github.com/torvalds/linux/blob/v5.4/drivers/thermal/thermal_core.c#=
L63


>
> > +             pr_err("Error: No cooling device type defined\n");
> >               return ERR_PTR(-EINVAL);
> > +     }
> > +
> > +     if (strlen(type) >=3D THERMAL_NAME_LENGTH) {
> > +             pr_err("Error: Cooling device name over %d chars: %s\n",
> > +                     THERMAL_NAME_LENGTH, type);
> > +             return ERR_PTR(-EINVAL);
> > +     }
> >
> >       if (!ops || !ops->get_max_state || !ops->get_cur_state ||
> > -         !ops->set_cur_state)
> > +         !ops->set_cur_state) {
> > +             pr_err("Error: Cooling device missing callbacks: %s\n", t=
ype);
> >               return ERR_PTR(-EINVAL);
> > +     }
> >
> >       cdev =3D kzalloc(sizeof(*cdev), GFP_KERNEL);
> >       if (!cdev)
> > @@ -972,7 +982,7 @@ __thermal_cooling_device_register(struct device_nod=
e *np,
> >       }
> >
> >       cdev->id =3D result;
> > -     strlcpy(cdev->type, type ? : "", sizeof(cdev->type));
> > +     strlcpy(cdev->type, type, sizeof(cdev->type));
> >       mutex_init(&cdev->lock);
> >       INIT_LIST_HEAD(&cdev->thermal_instances);
> >       cdev->np =3D np;
> >
>
>
> --
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