Re: [PATCH] gpio: Add support for GPIOF_ACTIVE_LOW to gpio_request_one

[Guenter Roeck]

On 07/16/2014 11:09 PM, Alexandre Courbot wrote:
> On Thu, Jul 17, 2014 at 8:11 AM, Guenter Roeck <linux@xxxxxxxxxxxx> wrote:
> > The gpio include file and the gpio documentation declare and document
> > GPIOF_ACTIVE_LOW as one of the flags to be passed to gpio_request_one
> > and related functions. However, the flag is not evaluated or used.
> >
> > Check the flag in gpio_request_one and set the gpio internal flag
> > FLAG_ACTIVE_LOW if it is set.
>
> What is the point since the integer GPIO API has no clue of the
> active-low status of a GPIO? It is only used by the gpiod and sysfs
> interfaces.

One can use gpio_request_one() to export a gpio pin to user space from
the kernel. That code path does use the flag, as you point out yourself above.

One could also argue that the integer gpio API _should_ support this as well,
but that is a different question.

Guenter

> > Signed-off-by: Guenter Roeck <linux@xxxxxxxxxxxx>
> > ---
> >   drivers/gpio/gpiolib.c | 3 +++
> >   1 file changed, 3 insertions(+)
> >
> > diff --git a/drivers/gpio/gpiolib.c b/drivers/gpio/gpiolib.c
> > index 2ebc907..43d9e34 100644
> > --- a/drivers/gpio/gpiolib.c
> > +++ b/drivers/gpio/gpiolib.c
> > @@ -1842,6 +1842,9 @@ int gpio_request_one(unsigned gpio, unsigned long flags, const char *label)
> >          if (flags & GPIOF_OPEN_SOURCE)
> >                  set_bit(FLAG_OPEN_SOURCE, &desc->flags);
> >
> > +       if (flags & GPIOF_ACTIVE_LOW)
> > +               set_bit(FLAG_ACTIVE_LOW, &desc->flags);
> > +
> >          if (flags & GPIOF_DIR_IN)
> >                  err = gpiod_direction_input(desc);
> >          else
> > --
> > 1.9.1

--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@xxxxxxxxxxxxxxx
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Please read the FAQ at  http://www.tux.org/lkml/