2014-06-06 11:02:45

by Lothar Waßmann

Subject: [PATCH] pwm-backlight:

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 <[email protected]>
---
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 38ca88b..3d265c4 100644
--- a/drivers/video/backlight/pwm_bl.c
+++ b/drivers/video/backlight/pwm_bl.c
@@ -178,7 +178,7 @@ static int pwm_backlight_parse_dt(struct device *dev,
data->dft_brightness = value;
data->max_brightness--;
}
-
+ data->enable_gpio = -EINVAL;
return 0;
}

--
1.7.10.4

2014-06-06 12:42:38

by Lee Jones

Subject: Re: [PATCH] pwm-backlight:

On Fri, 06 Jun 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 <[email protected]>
> ---
> 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 38ca88b..3d265c4 100644
> --- a/drivers/video/backlight/pwm_bl.c
> +++ b/drivers/video/backlight/pwm_bl.c
> @@ -178,7 +178,7 @@ static int pwm_backlight_parse_dt(struct device *dev,
> data->dft_brightness = value;
> data->max_brightness--;
> }
> -
> + data->enable_gpio = -EINVAL;
> return 0;
> }

This patch doesn't look like it will apply. I suggest you pull
v3.17-rc1 when it lands and rebase your patch.

--
Lee Jones
Linaro STMicroelectronics Landing Team Lead
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