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

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Date:   Fri, 19 Jun 2020 08:46:50 +0200
From:   Geert Uytterhoeven <geert@...ux-m68k.org>
To:     Guru Das Srinagesh <gurus@...eaurora.org>
Cc:     Thierry Reding <thierry.reding@...il.com>,
        Bartlomiej Zolnierkiewicz <b.zolnierkie@...sung.com>,
        Uwe Kleine-König 
        <u.kleine-koenig@...gutronix.de>, Lee Jones <lee.jones@...aro.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

Hi Guru,

On Thu, Jun 18, 2020 at 10:05 PM Guru Das Srinagesh
<gurus@...eaurora.org> wrote:
> On Wed, Jun 17, 2020 at 09:18:34AM +0200, Geert Uytterhoeven wrote:
> > 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.
>
> Hi Geert,
>
> Yes, this is already being done in the patch series [1] that forms the
> base for this specific patch.
>
> [1] https://lore.kernel.org/lkml/64f9ba1c9d6c49a397f12846493707883cee430f.1591136989.git.gurus@codeaurora.org/

IC, but the "will soon" suggested otherwise.
In any case, not combining both into a single patch causes a bisection
regression, regardless of the order in which they are applied.

Gr{oetje,eeting}s,

                        Geert

-- 
Geert Uytterhoeven -- There's lots of Linux beyond ia32 -- geert@...ux-m68k.org

In personal conversations with technical people, I call myself a hacker. But
when I'm talking to journalists I just say "programmer" or something like that.
                                -- Linus Torvalds