Patchwork pwm-backlight: fix bogus request for GPIO#0 when instantiated from DT

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Submitter Lothar Waßmann
Date Aug. 20, 2014, 6:38 a.m.
Message ID <1408516716-28828-1-git-send-email-LW@KARO-electronics.de>
Download mbox | patch
Permalink /patch/381549/
State Not Applicable
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Comments

Lothar Waßmann - Aug. 20, 2014, 6:38 a.m.
commit 257462dbf3ed ("pwm-backlight: switch to gpiod interface")
introduced a regression leading to acquiring a bogus GPIO-0 when
configured from DT without an 'enable-gpios' property.
The driver will happily accept the 0 initialized 'enable_gpio' member
of the struct platform_pwm_backlight_data as valid gpio number, and
request this GPIO as enable pin. In case of multiple driver instances,
the second will fail to register with the error message:
pwm-backlight backlight1.23: failed to request GPIO#0: -16

Fix this by setting enable_gpio in the pdata struct to -EINVAL.

Signed-off-by: Lothar Waßmann <LW@KARO-electronics.de>
---
 drivers/video/backlight/pwm_bl.c |    2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)
Thierry Reding - Aug. 20, 2014, 7:32 a.m.
On Wed, Aug 20, 2014 at 08:38:36AM +0200, Lothar Waßmann wrote:
> commit 257462dbf3ed ("pwm-backlight: switch to gpiod interface")
> introduced a regression leading to acquiring a bogus GPIO-0 when
> configured from DT without an 'enable-gpios' property.
> The driver will happily accept the 0 initialized 'enable_gpio' member
> of the struct platform_pwm_backlight_data as valid gpio number, and
> request this GPIO as enable pin. In case of multiple driver instances,
> the second will fail to register with the error message:
> pwm-backlight backlight1.23: failed to request GPIO#0: -16
> 
> Fix this by setting enable_gpio in the pdata struct to -EINVAL.
> 
> Signed-off-by: Lothar Waßmann <LW@KARO-electronics.de>
> ---
>  drivers/video/backlight/pwm_bl.c |    2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/drivers/video/backlight/pwm_bl.c b/drivers/video/backlight/pwm_bl.c
> index d7a3d13..e6ef6b4 100644
> --- a/drivers/video/backlight/pwm_bl.c
> +++ b/drivers/video/backlight/pwm_bl.c
> @@ -172,7 +172,7 @@ static int pwm_backlight_parse_dt(struct device *dev,
>  		data->dft_brightness = value;
>  		data->max_brightness--;
>  	}
> -
> +	data->enable_gpio = -EINVAL;

I'd prefer to keep the blank line for readability. Other than that:

Acked-by: Thierry Reding <treding@nvidia.com>
Lee Jones - Aug. 20, 2014, 12:17 p.m.
On Wed, 20 Aug 2014, Lothar Waßmann wrote:

> commit 257462dbf3ed ("pwm-backlight: switch to gpiod interface")
> introduced a regression leading to acquiring a bogus GPIO-0 when
> configured from DT without an 'enable-gpios' property.
> The driver will happily accept the 0 initialized 'enable_gpio' member
> of the struct platform_pwm_backlight_data as valid gpio number, and
> request this GPIO as enable pin. In case of multiple driver instances,
> the second will fail to register with the error message:
> pwm-backlight backlight1.23: failed to request GPIO#0: -16
> 
> Fix this by setting enable_gpio in the pdata struct to -EINVAL.
> 
> Signed-off-by: Lothar Waßmann <LW@KARO-electronics.de>
> ---
>  drivers/video/backlight/pwm_bl.c |    2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)

Applied to -fixes with Thierry's Ack and the blank line left.

> diff --git a/drivers/video/backlight/pwm_bl.c b/drivers/video/backlight/pwm_bl.c
> index d7a3d13..e6ef6b4 100644
> --- a/drivers/video/backlight/pwm_bl.c
> +++ b/drivers/video/backlight/pwm_bl.c
> @@ -172,7 +172,7 @@ static int pwm_backlight_parse_dt(struct device *dev,
>  		data->dft_brightness = value;
>  		data->max_brightness--;
>  	}
> -
> +	data->enable_gpio = -EINVAL;
>  	return 0;
>  }
>

Patch

diff --git a/drivers/video/backlight/pwm_bl.c b/drivers/video/backlight/pwm_bl.c
index d7a3d13..e6ef6b4 100644
--- a/drivers/video/backlight/pwm_bl.c
+++ b/drivers/video/backlight/pwm_bl.c
@@ -172,7 +172,7 @@  static int pwm_backlight_parse_dt(struct device *dev,
 		data->dft_brightness = value;
 		data->max_brightness--;
 	}
-
+	data->enable_gpio = -EINVAL;
 	return 0;
 }