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From:   Geert Uytterhoeven <geert@linux-m68k.org>
Date:   Wed, 6 Nov 2019 13:38:29 +0100
Message-ID: <CAMuHMdXQ_MP0j1saU1KdQwG5ooA5N5x0=MjJJX+p4EN1e11K-A@mail.gmail.com>
Subject: Re: [PATCH 13/62] gpio: gpio-f7188x: Use new GPIO_LINE_DIRECTION
To:     "Vaittinen, Matti" <Matti.Vaittinen@fi.rohmeurope.com>
Cc:     "simon.guinot@sequanux.org" <simon.guinot@sequanux.org>,
        "mazziesaccount@gmail.com" <mazziesaccount@gmail.com>,
        "linux-gpio@vger.kernel.org" <linux-gpio@vger.kernel.org>,
        "bgolaszewski@baylibre.com" <bgolaszewski@baylibre.com>,
        "linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
        "linus.walleij@linaro.org" <linus.walleij@linaro.org>
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Sender: linux-kernel-owner@vger.kernel.org
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Hi Matti,

On Wed, Nov 6, 2019 at 7:45 AM Vaittinen, Matti
<Matti.Vaittinen@fi.rohmeurope.com> wrote:
> On Wed, 2019-11-06 at 06:34 +0100, Simon Guinot wrote:
> > On Tue, Nov 05, 2019 at 12:16:03PM +0200, Matti Vaittinen wrote:
> > > It's hard for occasional GPIO code reader/writer to know if values
> > > 0/1
> > > equal to IN or OUT. Use defined GPIO_LINE_DIRECTION_IN and
> > > GPIO_LINE_DIRECTION_OUT to help them out.
> > >
> > > Signed-off-by: Matti Vaittinen <matti.vaittinen@fi.rohmeurope.com>
> > > ---
> > >  drivers/gpio/gpio-f7188x.c | 5 ++++-
> > >  1 file changed, 4 insertions(+), 1 deletion(-)
> > >
> > > diff --git a/drivers/gpio/gpio-f7188x.c b/drivers/gpio/gpio-
> > > f7188x.c
> > > index fdc639f856f1..cadd02993539 100644
> > > --- a/drivers/gpio/gpio-f7188x.c
> > > +++ b/drivers/gpio/gpio-f7188x.c
> > > @@ -250,7 +250,10 @@ static int f7188x_gpio_get_direction(struct
> > > gpio_chip *chip, unsigned offset)
> > >
> > >     superio_exit(sio->addr);
> > >
> > > -   return !(dir & 1 << offset);
> > > +   if (dir & 1 << offset)
> > > +           return GPIO_LINE_DIRECTION_OUT;
> > > +
> > > +   return GPIO_LINE_DIRECTION_IN
> >
> > Hi Matti,
> >
> > I am probably missing something but I can't find
> > GPIO_LINE_DIRECTION_IN
> > and GPIO_LINE_DIRECTION_OUT defined anywhere.
>
> Sorry. I accidentally sent the patch 01/62 to limited audience - and
> also messed up the message-ID from the series so threading messages is
> probably not working :( I did resend the patch adding defines to all
> reviewers yesterday - title should be "[RESEND PATCH 01/62] gpio: Add
> definition for GPIO direction".
>
> > Besides I am an occasional code reader/writer and I find the original
> > code easy to understand.
>
> Glad to hear that. When I read code:
>
> return !(dir & 1 << offset);
>
> It's impossible for me to tell if dir having bit at offset 'offset' set
> means IN or OUT - I know the meaning of code, it checks this bit for
> in/out - but which dir value is IN and which is OUT?
>
> When this is written as:
>
>         if (dir & 1 << offset)
>                 return GPIO_LINE_DIRECTION_OUT;
>
>         return GPIO_LINE_DIRECTION_IN
>
> it get's quite obvious even for me that having the matching bit set
> means direction to be OUT.

"suggest parentheses around... " warning?

    if (dir & BIT(offset))
            ...

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