linux-kernel - Re: [PATCH 4/6] pwm: pwm-lpc18xx-sct: test clock rate to avoid division by 0

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Date:	Wed, 2 Mar 2016 23:58:53 +0100
From:	Wolfram Sang <wsa@...-dreams.de>
To:	Joachim Eastwood <manabian@...il.com>
Cc:	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	linux-renesas-soc@...r.kernel.org,
	Thierry Reding <thierry.reding@...il.com>,
	linux-pwm@...r.kernel.org,
	"linux-arm-kernel@...ts.infradead.org" 
	<linux-arm-kernel@...ts.infradead.org>,
	Ariel D'Alessandro <ariel@...guardiasur.com.ar>
Subject: Re: [PATCH 4/6] pwm: pwm-lpc18xx-sct: test clock rate to avoid
 division by 0

On Wed, Mar 02, 2016 at 11:44:02PM +0100, Joachim Eastwood wrote:
> Hi Wolfram,
> 
> On 2 March 2016 at 23:33, Wolfram Sang <wsa@...-dreams.de> wrote:
> > From: Wolfram Sang <wsa+renesas@...g-engineering.com>
> >
> > The clk API may return 0 on clk_get_rate, so we should check the result before
> > using it as a divisor.
> >
> > Signed-off-by: Wolfram Sang <wsa+renesas@...g-engineering.com>
> > ---
> >
> > Should go individually via subsystem tree.
> >
> >  drivers/pwm/pwm-lpc18xx-sct.c | 2 ++
> >  1 file changed, 2 insertions(+)
> >
> > diff --git a/drivers/pwm/pwm-lpc18xx-sct.c b/drivers/pwm/pwm-lpc18xx-sct.c
> > index 9163085101bc94..6487962c355c03 100644
> > --- a/drivers/pwm/pwm-lpc18xx-sct.c
> > +++ b/drivers/pwm/pwm-lpc18xx-sct.c
> > @@ -360,6 +360,8 @@ static int lpc18xx_pwm_probe(struct platform_device *pdev)
> >         }
> >
> >         lpc18xx_pwm->clk_rate = clk_get_rate(lpc18xx_pwm->pwm_clk);
> > +       if (!lpc18xx_pwm->clk_rate)
> > +               return -EINVAL;
> 
> This needs to be:
> if (!lpc18xx_pwm->clk_rate) {
>     ret = -EINVAL;
>     goto disable_pwmclk;
> }

Yes, that slipped through. Thanks!

> I would also prefer an explicit check against 0 here. ie.:

Well, I like the reading "if not rate then error"

Will send V2 now...


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