[PATCH v7 3/9] backlight: gpio: explicitly set the direction of the GPIO
From: Bartosz Golaszewski
The GPIO backlight driver currently requests the line 'as is', without
acively setting its direction. This can lead to problems: if the line
is in input mode by default, we won't be able to drive it later when
updating the status and also reading its initial value doesn't make
sense for backlight setting.
Request the line 'as is' initially, so that we can read its value
without affecting it but then change the direction to output explicitly
when setting the initial brightness.
Also: check the current direction and only read the value if it's output.
Signed-off-by: Bartosz Golaszewski
---
drivers/video/backlight/gpio_backlight.c | 23 ++-
1 file changed, 18 insertions(+), 5 deletions(-)
diff --git a/drivers/video/backlight/gpio_backlight.c
b/drivers/video/backlight/gpio_backlight.c
index 3955b513f2f8..52f17c9ca1c3 100644
--- a/drivers/video/backlight/gpio_backlight.c
+++ b/drivers/video/backlight/gpio_backlight.c
@@ -25,9 +25,8 @@ struct gpio_backlight {
int def_value;
};
-static int gpio_backlight_update_status(struct backlight_device *bl)
+static int gpio_backlight_get_next_brightness(struct backlight_device *bl)
{
- struct gpio_backlight *gbl = bl_get_data(bl);
int brightness = bl->props.brightness;
if (bl->props.power != FB_BLANK_UNBLANK ||
@@ -35,6 +34,14 @@ static int gpio_backlight_update_status(struct
backlight_device *bl)
bl->props.state & (BL_CORE_SUSPENDED | BL_CORE_FBBLANK))
brightness = 0;
+ return brightness;
+}
+
+static int gpio_backlight_update_status(struct backlight_device *bl)
+{
+ struct gpio_backlight *gbl = bl_get_data(bl);
+ int brightness = gpio_backlight_get_next_brightness(bl);
+
gpiod_set_value_cansleep(gbl->gpiod, brightness);
return 0;
@@ -85,7 +92,8 @@ static int gpio_backlight_initial_power_state(struct
gpio_backlight *gbl)
return gbl->def_value ? FB_BLANK_UNBLANK : FB_BLANK_POWERDOWN;
/* if the enable GPIO is disabled, do not enable the backlight */
- if (gpiod_get_value_cansleep(gbl->gpiod) == 0)
+ if (gpiod_get_direction(gbl->gpiod) == 0 &&
+ gpiod_get_value_cansleep(gbl->gpiod) == 0)
return FB_BLANK_POWERDOWN;
return FB_BLANK_UNBLANK;
@@ -98,7 +106,7 @@ static int gpio_backlight_probe(struct platform_device *pdev)
struct backlight_properties props;
struct backlight_device *bl;
struct gpio_backlight *gbl;
- int ret;
+ int ret, init_brightness;
gbl = devm_kzalloc(>dev, sizeof(*gbl), GFP_KERNEL);
if (gbl == NULL)
@@ -151,7 +159,12 @@ static int gpio_backlight_probe(struct platform_device
*pdev)
bl->props.power = gpio_backlight_initial_power_state(gbl);
bl->props.brightness = 1;
- backlight_update_status(bl);
+ init_brightness = gpio_backlight_get_next_brightness(bl);
+ ret = gpiod_direction_output(gbl->gpiod, init_brightness);
+ if (ret) {
+ dev_err(>dev, "failed to set initial brightness\n");
+ return ret;
+ }
platform_set_drvdata(pdev, bl);
return 0;
--
2.23.0
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Re: [PATCH v7 3/9] backlight: gpio: explicitly set the direction of the GPIO
On Tue, Oct 22, 2019 at 10:36:24AM +0200, Bartosz Golaszewski wrote:
> From: Bartosz Golaszewski
>
> The GPIO backlight driver currently requests the line 'as is', without
> acively setting its direction. This can lead to problems: if the line
> is in input mode by default, we won't be able to drive it later when
> updating the status and also reading its initial value doesn't make
> sense for backlight setting.
>
> Request the line 'as is' initially, so that we can read its value
> without affecting it but then change the direction to output explicitly
> when setting the initial brightness.
>
> Also: check the current direction and only read the value if it's output.
>
> Signed-off-by: Bartosz Golaszewski
Reviewed-by: Daniel Thompson
> ---
> drivers/video/backlight/gpio_backlight.c | 23 ++-
> 1 file changed, 18 insertions(+), 5 deletions(-)
>
> diff --git a/drivers/video/backlight/gpio_backlight.c
> b/drivers/video/backlight/gpio_backlight.c
> index 3955b513f2f8..52f17c9ca1c3 100644
> --- a/drivers/video/backlight/gpio_backlight.c
> +++ b/drivers/video/backlight/gpio_backlight.c
> @@ -25,9 +25,8 @@ struct gpio_backlight {
> int def_value;
> };
>
> -static int gpio_backlight_update_status(struct backlight_device *bl)
> +static int gpio_backlight_get_next_brightness(struct backlight_device *bl)
> {
> - struct gpio_backlight *gbl = bl_get_data(bl);
> int brightness = bl->props.brightness;
>
> if (bl->props.power != FB_BLANK_UNBLANK ||
> @@ -35,6 +34,14 @@ static int gpio_backlight_update_status(struct
> backlight_device *bl)
> bl->props.state & (BL_CORE_SUSPENDED | BL_CORE_FBBLANK))
> brightness = 0;
>
> + return brightness;
> +}
> +
> +static int gpio_backlight_update_status(struct backlight_device *bl)
> +{
> + struct gpio_backlight *gbl = bl_get_data(bl);
> + int brightness = gpio_backlight_get_next_brightness(bl);
> +
> gpiod_set_value_cansleep(gbl->gpiod, brightness);
>
> return 0;
> @@ -85,7 +92,8 @@ static int gpio_backlight_initial_power_state(struct
> gpio_backlight *gbl)
> return gbl->def_value ? FB_BLANK_UNBLANK : FB_BLANK_POWERDOWN;
>
> /* if the enable GPIO is disabled, do not enable the backlight */
> - if (gpiod_get_value_cansleep(gbl->gpiod) == 0)
> + if (gpiod_get_direction(gbl->gpiod) == 0 &&
> + gpiod_get_value_cansleep(gbl->gpiod) == 0)
> return FB_BLANK_POWERDOWN;
>
> return FB_BLANK_UNBLANK;
> @@ -98,7 +106,7 @@ static int gpio_backlight_probe(struct platform_device
> *pdev)
> struct backlight_properties props;
> struct backlight_device *bl;
> struct gpio_backlight *gbl;
> - int ret;
> + int ret, init_brightness;
>
> gbl = devm_kzalloc(>dev, sizeof(*gbl), GFP_KERNEL);
> if (gbl == NULL)
> @@ -151,7 +159,12 @@ static int gpio_backlight_probe(struct platform_device
> *pdev)
> bl->props.power = gpio_backlight_initial_power_state(gbl);
> bl->props.brightness = 1;
>
> - backlight_update_status(bl);
> + init_brightness = gpio_backlight_get_next_brightness(bl);
> + ret = gpiod_direction_output(gbl->gpiod, init_brightness);
> + if (ret) {
> + dev_err(>dev, "failed to set initial brightness\n");
> + return ret;
> + }
>
> platform_set_drvdata(pdev, bl);
> return 0;
> --
> 2.23.0
>
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