Re: [PATCH] backlight: pwm_bl: Fix GPIO out for unimplemented .get_direction()

[Daniel Thompson]

On 24/03/17 16:42, Daniel Thompson wrote:
> On 22/03/17 17:21, Geert Uytterhoeven wrote:
> > Commit 7613c922315e308a ("backlight: pwm_bl: Move the checks for initial
> > power state to a separate function") not just moved some code, but made
> > slight changes in semantics.
> >
> > If a gpiochip doesn't implement the optional .get_direction() callback,
> > gpiod_get_direction always returns -EINVAL, which is never equal to
> > GPIOF_DIR_IN, leading to the GPIO not being configured for output.
> >
> > To avoid this, invert the test and check for not GPIOF_DIR_OUT instead,
> > like the original code did.
> >
> > This restores the display on r8a7740/armadillo.
> >
> > Fixes: 7613c922315e308a ("backlight: pwm_bl: Move the checks for
> > initial power state to a separate function")
> > Signed-off-by: Geert Uytterhoeven <geert+renesas@xxxxxxxxx>
>
> Acked-by: Daniel Thommpson <daniel.thompson@xxxxxxxxxx>

Actually, it would be better if there only one m...

Acked-by: Daniel Thompson <daniel.thompson@xxxxxxxxxx>


Daniel.

> > ---
> >  drivers/video/backlight/pwm_bl.c | 7 ++++---
> >  1 file changed, 4 insertions(+), 3 deletions(-)
> >
> > diff --git a/drivers/video/backlight/pwm_bl.c
> > b/drivers/video/backlight/pwm_bl.c
> > index d7efcb632f7d9dde..002f1ce22bd02032 100644
> > --- a/drivers/video/backlight/pwm_bl.c
> > +++ b/drivers/video/backlight/pwm_bl.c
> > @@ -297,14 +297,15 @@ static int pwm_backlight_probe(struct
> > platform_device *pdev)
> >      }
> >
> >      /*
> > -     * If the GPIO is configured as input, change the direction to
> > output
> > -     * and set the GPIO as active.
> > +     * If the GPIO is not known to be already configured as output, that
> > +     * is, if gpiod_get_direction returns either GPIOF_DIR_IN or
> > -EINVAL,
> > +     * change the direction to output and set the GPIO as active.
> >       * Do not force the GPIO to active when it was already output as it
> >       * could cause backlight flickering or we would enable the
> > backlight too
> >       * early. Leave the decision of the initial backlight state for
> > later.
> >       */
> >      if (pb->enable_gpio &&
> > -        gpiod_get_direction(pb->enable_gpio) == GPIOF_DIR_IN)
> > +        gpiod_get_direction(pb->enable_gpio) != GPIOF_DIR_OUT)
> >          gpiod_direction_output(pb->enable_gpio, 1);
> >
> >      pb->power_supply = devm_regulator_get(&pdev->dev, "power");