linux-kernel - Re: [PATCH v3 1/3] thermal: prevent cooling device with no type to be registered

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Message-ID: <CAGXk5yrvfJW62NHRHRJ4KtQEp5qxfr1V=R37kHMnkV9xgbEU3g@mail.gmail.com>
Date:   Mon, 9 Dec 2019 13:13:33 -0800
From:   Wei Wang <wvw@...gle.com>
To:     Daniel Lezcano <daniel.lezcano@...aro.org>
Cc:     Wei Wang <wei.vince.wang@...il.com>,
        Zhang Rui <rui.zhang@...el.com>,
        Eduardo Valentin <edubezval@...il.com>,
        Amit Kucheria <amit.kucheria@...durent.com>,
        Linux PM list <linux-pm@...r.kernel.org>,
        LKML <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH v3 1/3] thermal: prevent cooling device with no type to be registered

On Mon, Dec 9, 2019 at 11:36 AM Daniel Lezcano
<daniel.lezcano@...aro.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@...gle.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_core.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_node *np,
> >       struct thermal_zone_device *pos = NULL;
> >       int result;
> >
> > -     if (type && strlen(type) >= THERMAL_NAME_LENGTH)
> > +     if (!type || !type[0]) {
>
> Why not use strlen(type) == 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) >= 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", type);
> >               return ERR_PTR(-EINVAL);
> > +     }
> >
> >       cdev = kzalloc(sizeof(*cdev), GFP_KERNEL);
> >       if (!cdev)
> > @@ -972,7 +982,7 @@ __thermal_cooling_device_register(struct device_node *np,
> >       }
> >
> >       cdev->id = 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 = np;
> >
>
>
> --
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