linux-kernel - Re: [PATCH v2] gpiolib: return 0 or 1 in gpiod_get

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Date:	Mon, 30 Nov 2015 12:05:49 -0800
From:	Bjorn Andersson <bjorn@...o.se>
To:	Jose Diaz de Grenu de Pedro <Jose.DiazdeGrenudePedro@...i.com>
Cc:	"linux-gpio@...r.kernel.org" <linux-gpio@...r.kernel.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	Linus Walleij <linus.walleij@...aro.org>,
	Alexandre Courbot <gnurou@...il.com>, hector.palacios@...i.com
Subject: Re: [PATCH v2] gpiolib: return 0 or 1 in gpiod_get_value*() functions

On Mon, Nov 30, 2015 at 9:30 AM, Jose Diaz de Grenu de Pedro
<Jose.DiazdeGrenudePedro@...i.com> wrote:
> Commit 79a9becda894 moved the awareness of active low state
> into the gpiod_get_value*() functions, but it only inverts the
> GPIO's raw value when it is active low. If the GPIO is active
> high, the gpiod_get_value*() functions return the raw value of
> the register, which can be any positive value.
>
> This patch does a double inversion when the GPIO is active high
> to make sure either 0 or 1 is returned by these functions.
>
> Signed-off-by: Jose Diaz de Grenu de Pedro <Jose.DiazdeGrenudePedro@...i.com>
> Signed-off-by: Hector Palacios <hector.palacios@...i.com>
> ---
> change in v2:
>  - add missing semicolon
> ---
>  drivers/gpio/gpiolib.c | 12 ++++++------
>  1 file changed, 6 insertions(+), 6 deletions(-)
>
> diff --git a/drivers/gpio/gpiolib.c b/drivers/gpio/gpiolib.c
> index 50c4922fe53a..bd96f0457ba8 100644
> --- a/drivers/gpio/gpiolib.c
> +++ b/drivers/gpio/gpiolib.c
> @@ -1981,9 +1981,9 @@ int gpiod_get_value(const struct gpio_desc *desc)
>
>         value = _gpiod_get_raw_value(desc);
>         if (test_bit(FLAG_ACTIVE_LOW, &desc->flags))
> -               value = !value;
> -
> -       return value;
> +               return !value;
> +       else
> +               return !!value;
>  }
>  EXPORT_SYMBOL_GPL(gpiod_get_value);

On linux-next (at least) _gpiod_get_raw_value() returns the following value:

value = value < 0 ? value : !!value;

So this should already be negative errno, 0 or 1.

Regards,
Bjorn
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