linux-kernel - Re: [PATCH 1/2] video: ssd1307fb: Print PWM period using 64-bit format specifier

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Date:   Wed, 17 Jun 2020 19:30:31 +0200
From:   Uwe Kleine-König <u.kleine-koenig@...gutronix.de>
To:     Geert Uytterhoeven <geert@...ux-m68k.org>
Cc:     Thierry Reding <thierry.reding@...il.com>,
        Bartlomiej Zolnierkiewicz <b.zolnierkie@...sung.com>,
        Lee Jones <lee.jones@...aro.org>,
        Guru Das Srinagesh <gurus@...eaurora.org>,
        Linux PWM List <linux-pwm@...r.kernel.org>,
        Linux Fbdev development list <linux-fbdev@...r.kernel.org>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH 1/2] video: ssd1307fb: Print PWM period using 64-bit
 format specifier

On Wed, Jun 17, 2020 at 09:18:34AM +0200, Geert Uytterhoeven wrote:
> Hi Thierry,
> 
> On Mon, Jun 15, 2020 at 4:17 PM Thierry Reding <thierry.reding@...il.com> wrote:
> > The PWM core will soon change the duty cycle and period of PWMs to 64
> > bits to allow for a broader range of values. Use a 64-bit format
> > specifier to avoid a warning when that change is made.
> >
> > Signed-off-by: Thierry Reding <thierry.reding@...il.com>
> 
> > --- a/drivers/video/fbdev/ssd1307fb.c
> > +++ b/drivers/video/fbdev/ssd1307fb.c
> > @@ -312,7 +312,7 @@ static int ssd1307fb_init(struct ssd1307fb_par *par)
> >                 /* Enable the PWM */
> >                 pwm_enable(par->pwm);
> >
> > -               dev_dbg(&par->client->dev, "Using PWM%d with a %dns period.\n",
> > +               dev_dbg(&par->client->dev, "Using PWM%d with a %lluns period.\n",
> >                         par->pwm->pwm, pwm_get_period(par->pwm));
> >         }
> 
> This change must be done together with changing the return type of
> pwm_get_period(), else you will get a compiler warning, and will print a
> bogus value.

Right, or we must change to passing (unsigned long
long)pwm_get_period(par->pwm), then change the prototype and then drop
the cast again.

Best regards
Uwe

-- 
Pengutronix e.K.                           | Uwe Kleine-König            |
Industrial Linux Solutions                 | https://www.pengutronix.de/ |

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