# \[PATCH\] backlight: pwm\_bl: Fix GPIO out for unimplemented .get\_direction() - Subsystems: FRAMEBUFFER LAYER, BACKLIGHT CLASS/SUBSYSTEM, THE REST - Maintainers: Helge Deller, Lee Jones, Daniel Thompson, Jingoo Han, Linus Torvalds - List: linux-fbdev - 6 messages, 5 authors - Page: https://ratatoskr.run/linux-fbdev/2017/03/4960938/t ## \[PATCH\] backlight: pwm\_bl: Fix GPIO out for unimplemented .get\_direction() - From: Geert Uytterhoeven \ - Date: 2017-03-22 17:21:55 - Message: https://ratatoskr.run/linux-fbdev/2017/03/4960938.md ```text 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 --- 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"); -- 2.7.4 ``` ## Re: \[PATCH\] backlight: pwm\_bl: Fix GPIO out for unimplemented .get\_direction() - From: Peter Ujfalusi \ - Date: 2017-03-23 21:13:56 - Message: https://ratatoskr.run/linux-fbdev/2017/03/4962111.md ```text On 03/22/2017 07:21 PM, 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. The platforms I have tested the gpio drivers do implement the get_direction() callback and I was not aware of this behaviour. > 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 Reviewed-by: Peter Ujfalusi > --- > 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"); > -- Péter ``` ## Re: \[PATCH\] backlight: pwm\_bl: Fix GPIO out for unimplemented .get\_direction() - From: Philipp Zabel \ - Date: 2017-03-24 09:13:47 - Message: https://ratatoskr.run/linux-fbdev/2017/03/4962441.md ```text On Wed, 2017-03-22 at 18:21 +0100, 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 Acked-by: Philipp Zabel regards Philipp > --- > 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"); ``` ## Re: \[PATCH\] backlight: pwm\_bl: Fix GPIO out for unimplemented .get\_direction() - From: Daniel Thompson \ - Date: 2017-03-24 16:43:07 - Message: https://ratatoskr.run/linux-fbdev/2017/03/4962856.md ```text 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 Acked-by: Daniel Thommpson > --- > 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"); > ``` ## Re: \[PATCH\] backlight: pwm\_bl: Fix GPIO out for unimplemented .get\_direction() - From: Daniel Thompson \ - Date: 2017-03-24 16:43:58 - Message: https://ratatoskr.run/linux-fbdev/2017/03/4962857.md ```text 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 > > Acked-by: Daniel Thommpson Actually, it would be better if there only one m... Acked-by: Daniel Thompson 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"); >> > ``` ## Re: \[PATCH\] backlight: pwm\_bl: Fix GPIO out for unimplemented .get\_direction() - From: Lee Jones \ - Date: 2017-03-27 14:28:00 - Message: https://ratatoskr.run/linux-fbdev/2017/03/4964145.md ```text On Fri, 24 Mar 2017, Daniel Thompson wrote: > 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 > > > > Acked-by: Daniel Thommpson > > Actually, it would be better if there only one m... > > Acked-by: Daniel Thompson You probably don't want to be typing out your Acks manually every time. Can you set a key combination in your editor? > > > --- > > > 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"); > > > > > > -- Lee Jones Linaro STMicroelectronics Landing Team Lead Linaro.org │ Open source software for ARM SoCs Follow Linaro: Facebook | Twitter | Blog ```