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From:   Geert Uytterhoeven <geert@linux-m68k.org>
Date:   Mon, 19 Jul 2021 10:40:32 +0200
Message-ID: <CAMuHMdXZcaR28fUuiNWF8jv-NnOYkAXxR8z+vOQ2rY3BqQMWTQ@mail.gmail.com>
Subject: Re: [PATCH 1/2] swap led_brightness from enum to typedef
To:     Amy Parker <apark0006@student.cerritos.edu>
Cc:     Pavel Machek <pavel@ucw.cz>,
        linux-leds <linux-leds@vger.kernel.org>,
        Linux Kernel Mailing List <linux-kernel@vger.kernel.org>,
        Dan Carpenter <dan.carpenter@oracle.com>
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On Mon, Jul 19, 2021 at 9:18 AM Geert Uytterhoeven <geert@linux-m68k.org> wrote:
> On Thu, 15 Jul 2021, Amy Parker wrote:
> > This commit changes how led_brightness, declared in header file
> > include/linux/leds.h, works throughout the kernel, and updates other
> > files in accordance.
> >
> > The TODO located at drivers/leds/TODO requests:
> >
> > * Get rid of led_brightness
> >
> > It is really an integer, as maximum is configurable. Get rid of it, or
> > make it into typedef or something.
> >
> > This patch changes the declaration of led_brightness from an enum to a
> > typedef. In order to hold the currently existing enum values, macro
> > definitions are provided. Files which use led_brightness are updated to
> > conform to the new types.
> >
> > Signed-off-by: Amy Parker <apark0006@student.cerritos.edu>
>
> Thanks for your patch!
>
> > 207 files changed, 437 insertions(+), 438 deletions(-)
>
> This touches a lot of files, so we better get it right.
>
> > --- a/include/linux/leds.h
> > +++ b/include/linux/leds.h
> > @@ -26,12 +26,11 @@ struct device_node;
> >  */
> >
> > /* This is obsolete/useless. We now support variable maximum brightness. */
> > -enum led_brightness {
> > -     LED_OFF         = 0,
> > -     LED_ON          = 1,
> > -     LED_HALF        = 127,
> > -     LED_FULL        = 255,
> > -};
> > +typedef u8 led_brightness;
>
> In general, typedefs are frowned upon in the kernel, but there can be a
> good reason to use one.
> What if the maximum brightness is larger than 255?
> Using "unsigned int" sounds better to me, but let's wait for Pavel...

And as Dan just pointed out, "signed int" would be even better, as it
would allow a function to return an error code.

> > +#define LED_OFF 0
> > +#define LED_ON 1
> > +#define LED_HALF 127
> > +#define LED_FULL 255

Gr{oetje,eeting}s,

                        Geert

-- 
Geert Uytterhoeven -- There's lots of Linux beyond ia32 -- geert@linux-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