Re: [PATCH v3 2/5] thermal: rockchip: fix a impossible condition caused by the warning

Brian Norris
2015-12-03T20:34:03Z

On Thu, Dec 03, 2015 at 12:19:08PM -0800, Dmitry Torokhov wrote:
> On Thu, Dec 03, 2015 at 04:48:40PM +0800, Caesar Wang wrote:
> > As the Dan report the smatch check the thermal driver warning:
> > drivers/thermal/rockchip_thermal.c:551 rockchip_configure_from_dt()
> > warn: impossible condition '(thermal->tshut_temp > ((~0 >> 1))) =>
> > (s32min-s32max > s32max)'
> >
> > Let's we remove the imposssible condition Since the Temperature is
> > currently represented as int not long in the thermal driver.
> >
> > Fixes: commit 437df2172e8d
> > ("thermal: rockchip: consistently use int for temperatures")
> >
> > Reported-by: Dan Carpenter <dan.carpenter@oracle.com>
> > Signed-off-by: Caesar Wang <wxt@rock-chips.com>
> >
> > ---
> >
> > Changes in v3:
> > - As Brian comments on https://patchwork.kernel.org/patch/7580661/,
> > let's remove the impossible condition.
> >
> > Changes in v2: None
> > Changes in v1: None
> >
> > drivers/thermal/rockchip_thermal.c | 6 ------
> > 1 file changed, 6 deletions(-)
> >
> > diff --git a/drivers/thermal/rockchip_thermal.c b/drivers/thermal/rockchip_thermal.c
> > index ae796ec..611de00 100644
> > --- a/drivers/thermal/rockchip_thermal.c
> > +++ b/drivers/thermal/rockchip_thermal.c
> > @@ -549,12 +549,6 @@ static int rockchip_configure_from_dt(struct device *dev,
> > thermal->tshut_temp = shut_temp;
> > }
> >
> > - if (thermal->tshut_temp > INT_MAX) {
> > - dev_err(dev, "Invalid tshut temperature specified: %d\n",
> > - thermal->tshut_temp);
> > - return -ERANGE;
> > - }
>
> Well, that is not entirely correct. The value that we read from DT is
> u32, but we convert it down to int. I believe you want to move the check

Do we really account for the possibility of sizeof(int) < sizeof(u32)?

EDIT: A bit after writing the above line, I notice my error, but in case
anyone else is thinking the same thing... I guess you're referring to
the sign bit, since we're casting unsigned to signed.

Brian

> up so that you do:
>
> } else if (tshut_temp > INT_MAX) {
> dev_err(dev, "Invalid tshut temperature specified: %d\n",
> thermal->tshut_temp);
> return -ERANGE;
> } else {
> thermal->tshut_temp = shut_temp;
> }
>
> Thanks.