[PATCH] pwm_backlight: pass correct brightness to callback

[PATCH] pwm_backlight: pass correct brightness to callback

[Alexandre Courbot]

pwm_backlight_update_status calls two callbacks before and after
applying the new PWM settings. However, the brightness scale is
completely changed in between if brightness levels are used. This patch
ensures that both callbacks are passed brightness values of the same
meaning.

Signed-off-by: Alexandre Courbot <acourbot@nvidia.com>
---
 drivers/video/backlight/pwm_bl.c | 12 +++++++-----
 1 file changed, 7 insertions(+), 5 deletions(-)

diff --git a/drivers/video/backlight/pwm_bl.c b/drivers/video/backlight/pwm_bl.c
index 057389d..dd4d24d 100644
--- a/drivers/video/backlight/pwm_bl.c
+++ b/drivers/video/backlight/pwm_bl.c
@@ -39,6 +39,7 @@ static int pwm_backlight_update_status(struct backlight_device *bl)
 {
 	struct pwm_bl_data *pb = dev_get_drvdata(&bl->dev);
 	int brightness = bl->props.brightness;
+	int pwm_brightness;
 	int max = bl->props.max_brightness;
 
 	if (bl->props.power != FB_BLANK_UNBLANK)
@@ -55,13 +56,14 @@ static int pwm_backlight_update_status(struct backlight_device *bl)
 		pwm_disable(pb->pwm);
 	} else {
 		if (pb->levels) {
-			brightness = pb->levels[brightness];
+			pwm_brightness = pb->levels[brightness];
 			max = pb->levels[max];
-		}
+		} else
+			pwm_brightness = brightness;
 
-		brightness = pb->lth_brightness +
-			(brightness * (pb->period - pb->lth_brightness) / max);
-		pwm_config(pb->pwm, brightness, pb->period);
+		pwm_brightness = pb->lth_brightness +
+		     (pwm_brightness * (pb->period - pb->lth_brightness) / max);
+		pwm_config(pb->pwm, pwm_brightness, pb->period);
 		pwm_enable(pb->pwm);
 	}
 
-- 
1.7.11.1

Re: [PATCH] pwm_backlight: pass correct brightness to callback

[Thierry Reding]

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On Mon, Jul 09, 2012 at 01:21:40PM +0900, Alexandre Courbot wrote:
> pwm_backlight_update_status calls two callbacks before and after
> applying the new PWM settings. However, the brightness scale is
> completely changed in between if brightness levels are used. This patch
> ensures that both callbacks are passed brightness values of the same
> meaning.
> 
> Signed-off-by: Alexandre Courbot <acourbot@nvidia.com>
> ---
>  drivers/video/backlight/pwm_bl.c | 12 +++++++-----
>  1 file changed, 7 insertions(+), 5 deletions(-)

I had to actually read this patch a number of times and then realized I
was completely missing the context. Looking at the whole function makes
it more obvious what you mean.

However I think it'd be much clearer if we just passed the value of
bl->props.brightness into the callbacks, that way we can avoid the
additional variable.

Thierry

> 
> diff --git a/drivers/video/backlight/pwm_bl.c b/drivers/video/backlight/pwm_bl.c
> index 057389d..dd4d24d 100644
> --- a/drivers/video/backlight/pwm_bl.c
> +++ b/drivers/video/backlight/pwm_bl.c
> @@ -39,6 +39,7 @@ static int pwm_backlight_update_status(struct backlight_device *bl)
>  {
>  	struct pwm_bl_data *pb = dev_get_drvdata(&bl->dev);
>  	int brightness = bl->props.brightness;
> +	int pwm_brightness;
>  	int max = bl->props.max_brightness;
>  
>  	if (bl->props.power != FB_BLANK_UNBLANK)
> @@ -55,13 +56,14 @@ static int pwm_backlight_update_status(struct backlight_device *bl)
>  		pwm_disable(pb->pwm);
>  	} else {
>  		if (pb->levels) {
> -			brightness = pb->levels[brightness];
> +			pwm_brightness = pb->levels[brightness];
>  			max = pb->levels[max];
> -		}
> +		} else
> +			pwm_brightness = brightness;
>  
> -		brightness = pb->lth_brightness +
> -			(brightness * (pb->period - pb->lth_brightness) / max);
> -		pwm_config(pb->pwm, brightness, pb->period);
> +		pwm_brightness = pb->lth_brightness +
> +		     (pwm_brightness * (pb->period - pb->lth_brightness) / max);
> +		pwm_config(pb->pwm, pwm_brightness, pb->period);
>  		pwm_enable(pb->pwm);
>  	}
>  
> -- 
> 1.7.11.1
> 
> 

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Re: [PATCH] pwm_backlight: pass correct brightness to callback

[Alex Courbot]

On 07/09/2012 02:10 PM, Thierry Reding wrote:
> I had to actually read this patch a number of times and then realized I
> was completely missing the context. Looking at the whole function makes
> it more obvious what you mean.
>
> However I think it'd be much clearer if we just passed the value of
> bl->props.brightness into the callbacks, that way we can avoid the
> additional variable.

This won't work I'm afraid, as brightness can be modified prior to being 
passed to the callback function:

	if (bl->props.power != FB_BLANK_UNBLANK)
		brightness = 0;

	if (bl->props.fb_blank != FB_BLANK_UNBLANK)
		brightness = 0;

	if (pb->notify)
		brightness = pb->notify(pb->dev, brightness);

Alex.

[PATCHv2] pwm_backlight: pass correct brightness to callback

[Alexandre Courbot]

pwm_backlight_update_status calls the notify() and notify_after()
callbacks before and after applying the new PWM settings. However, if
brightness levels are used, the brightness value will be changed from
the index into the levels array to the PWM duty cycle length before
being passed to notify_after(), which results in inconsistent behavior.

Signed-off-by: Alexandre Courbot <acourbot@nvidia.com>
---
 drivers/video/backlight/pwm_bl.c | 11 +++++++----
 1 file changed, 7 insertions(+), 4 deletions(-)

diff --git a/drivers/video/backlight/pwm_bl.c b/drivers/video/backlight/pwm_bl.c
index 057389d..6d1d3ea 100644
--- a/drivers/video/backlight/pwm_bl.c
+++ b/drivers/video/backlight/pwm_bl.c
@@ -39,6 +39,7 @@ static int pwm_backlight_update_status(struct backlight_device *bl)
 {
 	struct pwm_bl_data *pb = dev_get_drvdata(&bl->dev);
 	int brightness = bl->props.brightness;
+	int pwm_brightness;
 	int max = bl->props.max_brightness;
 
 	if (bl->props.power != FB_BLANK_UNBLANK)
@@ -55,13 +56,15 @@ static int pwm_backlight_update_status(struct backlight_device *bl)
 		pwm_disable(pb->pwm);
 	} else {
 		if (pb->levels) {
-			brightness = pb->levels[brightness];
+			pwm_brightness = pb->levels[brightness];
 			max = pb->levels[max];
+		} else {
+			pwm_brightness = brightness;
 		}
 
-		brightness = pb->lth_brightness +
-			(brightness * (pb->period - pb->lth_brightness) / max);
-		pwm_config(pb->pwm, brightness, pb->period);
+		pwm_brightness = pb->lth_brightness +
+		     (pwm_brightness * (pb->period - pb->lth_brightness) / max);
+		pwm_config(pb->pwm, pwm_brightness, pb->period);
 		pwm_enable(pb->pwm);
 	}
 
-- 
1.7.11.1

[PATCHv3] pwm_backlight: pass correct brightness to callback

[Alexandre Courbot]

pwm_backlight_update_status calls the notify() and notify_after()
callbacks before and after applying the new PWM settings. However, if
brightness levels are used, the brightness value will be changed from
the index into the levels array to the PWM duty cycle length before
being passed to notify_after(), which results in inconsistent behavior.

Signed-off-by: Alexandre Courbot <acourbot@nvidia.com>
---
 drivers/video/backlight/pwm_bl.c | 11 +++++++----
 1 file changed, 7 insertions(+), 4 deletions(-)

diff --git a/drivers/video/backlight/pwm_bl.c b/drivers/video/backlight/pwm_bl.c
index 057389d..be48517 100644
--- a/drivers/video/backlight/pwm_bl.c
+++ b/drivers/video/backlight/pwm_bl.c
@@ -54,14 +54,17 @@ static int pwm_backlight_update_status(struct backlight_device *bl)
 		pwm_config(pb->pwm, 0, pb->period);
 		pwm_disable(pb->pwm);
 	} else {
+		int duty_cycle;
 		if (pb->levels) {
-			brightness = pb->levels[brightness];
+			duty_cycle = pb->levels[brightness];
 			max = pb->levels[max];
+		} else {
+			duty_cycle = brightness;
 		}
 
-		brightness = pb->lth_brightness +
-			(brightness * (pb->period - pb->lth_brightness) / max);
-		pwm_config(pb->pwm, brightness, pb->period);
+		duty_cycle = pb->lth_brightness +
+		     (duty_cycle * (pb->period - pb->lth_brightness) / max);
+		pwm_config(pb->pwm, duty_cycle, pb->period);
 		pwm_enable(pb->pwm);
 	}
 
-- 
1.7.11.1

Re: [PATCHv3] pwm_backlight: pass correct brightness to callback

[Thierry Reding]

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On Mon, Jul 09, 2012 at 03:04:23PM +0900, Alexandre Courbot wrote:
> pwm_backlight_update_status calls the notify() and notify_after()
> callbacks before and after applying the new PWM settings. However, if
> brightness levels are used, the brightness value will be changed from
> the index into the levels array to the PWM duty cycle length before
> being passed to notify_after(), which results in inconsistent behavior.
> 
> Signed-off-by: Alexandre Courbot <acourbot@nvidia.com>
> ---
>  drivers/video/backlight/pwm_bl.c | 11 +++++++----
>  1 file changed, 7 insertions(+), 4 deletions(-)

Applied, with a minor stylistic fixup adding a blank line after the
duty_cycle variable declaration. Thanks.

Thierry

> diff --git a/drivers/video/backlight/pwm_bl.c b/drivers/video/backlight/pwm_bl.c
> index 057389d..be48517 100644
> --- a/drivers/video/backlight/pwm_bl.c
> +++ b/drivers/video/backlight/pwm_bl.c
> @@ -54,14 +54,17 @@ static int pwm_backlight_update_status(struct backlight_device *bl)
>  		pwm_config(pb->pwm, 0, pb->period);
>  		pwm_disable(pb->pwm);
>  	} else {
> +		int duty_cycle;
>  		if (pb->levels) {
> -			brightness = pb->levels[brightness];
> +			duty_cycle = pb->levels[brightness];
>  			max = pb->levels[max];
> +		} else {
> +			duty_cycle = brightness;
>  		}
>  
> -		brightness = pb->lth_brightness +
> -			(brightness * (pb->period - pb->lth_brightness) / max);
> -		pwm_config(pb->pwm, brightness, pb->period);
> +		duty_cycle = pb->lth_brightness +
> +		     (duty_cycle * (pb->period - pb->lth_brightness) / max);
> +		pwm_config(pb->pwm, duty_cycle, pb->period);
>  		pwm_enable(pb->pwm);
>  	}
>  
> -- 
> 1.7.11.1
> 
> 
> 

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RE: [PATCH] pwm_backlight: pass correct brightness to callback

[Jingoo Han]

On Monday, July 09, 2012 1:22 PM, Alexandre Courbot wrote:

> pwm_backlight_update_status calls two callbacks before and after
> applying the new PWM settings. However, the brightness scale is
> completely changed in between if brightness levels are used. This patch
> ensures that both callbacks are passed brightness values of the same
> meaning.
> 
> Signed-off-by: Alexandre Courbot <acourbot@nvidia.com>
> ---
>  drivers/video/backlight/pwm_bl.c | 12 +++++++-----
>  1 file changed, 7 insertions(+), 5 deletions(-)
> 
> diff --git a/drivers/video/backlight/pwm_bl.c b/drivers/video/backlight/pwm_bl.c
> index 057389d..dd4d24d 100644
> --- a/drivers/video/backlight/pwm_bl.c
> +++ b/drivers/video/backlight/pwm_bl.c
> @@ -39,6 +39,7 @@ static int pwm_backlight_update_status(struct backlight_device *bl)
>  {
>  	struct pwm_bl_data *pb = dev_get_drvdata(&bl->dev);
>  	int brightness = bl->props.brightness;
> +	int pwm_brightness;
>  	int max = bl->props.max_brightness;
> 
>  	if (bl->props.power != FB_BLANK_UNBLANK)
> @@ -55,13 +56,14 @@ static int pwm_backlight_update_status(struct backlight_device *bl)
>  		pwm_disable(pb->pwm);
>  	} else {
>  		if (pb->levels) {
> -			brightness = pb->levels[brightness];
> +			pwm_brightness = pb->levels[brightness];
>  			max = pb->levels[max];
> -		}
> +		} else
> +			pwm_brightness = brightness;

Hi Alexandre Courbot,

Please, use braces to keep the Coding Style.
Refer to Documentation/CodingStyle as follow:

169 This does not apply if only one branch of a conditional statement is a single
170 statement; in the latter case use braces in both branches:
171
172 if (condition) {
173         do_this();
174         do_that();
175 } else {
176         otherwise();
177 }

Best regards,
Jingoo Han

> 
> -		brightness = pb->lth_brightness +
> -			(brightness * (pb->period - pb->lth_brightness) / max);
> -		pwm_config(pb->pwm, brightness, pb->period);
> +		pwm_brightness = pb->lth_brightness +
> +		     (pwm_brightness * (pb->period - pb->lth_brightness) / max);
> +		pwm_config(pb->pwm, pwm_brightness, pb->period);
>  		pwm_enable(pb->pwm);
>  	}
> 
> --
> 1.7.11.1
> 
> --
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