diff mbox series

backlight: propagate errors from get_brightness()

Message ID 20210906215525.15418-1-linux@weissschuh.net (mailing list archive)
State New, archived
Headers show
Series backlight: propagate errors from get_brightness() | expand

Commit Message

Thomas Weißschuh Sept. 6, 2021, 9:55 p.m. UTC
backlight.h documents "struct backlight_ops->get_brightness()" to return
a negative errno on failure.
So far these errors have not been handled in the backlight core.
This leads to negative values being exposed through sysfs although only
positive values are documented to be reported.

Signed-off-by: Thomas Weißschuh <linux@weissschuh.net>
---
 drivers/video/backlight/backlight.c | 22 +++++++++++++++++-----
 1 file changed, 17 insertions(+), 5 deletions(-)


base-commit: 79fad92f2e596f5a8dd085788a24f540263ef887

Comments

Daniel Thompson Sept. 7, 2021, 9:31 a.m. UTC | #1
On Mon, Sep 06, 2021 at 11:55:25PM +0200, Thomas Weißschuh wrote:
> backlight.h documents "struct backlight_ops->get_brightness()" to return
> a negative errno on failure.
> So far these errors have not been handled in the backlight core.
> This leads to negative values being exposed through sysfs although only
> positive values are documented to be reported.
> 
> Signed-off-by: Thomas Weißschuh <linux@weissschuh.net>

Change looks good overall but I've raised a few quibbles about the new
error message below.


> ---
>  drivers/video/backlight/backlight.c | 22 +++++++++++++++++-----
>  1 file changed, 17 insertions(+), 5 deletions(-)
> 
> diff --git a/drivers/video/backlight/backlight.c b/drivers/video/backlight/backlight.c
> index 537fe1b376ad..d681962f8509 100644
> --- a/drivers/video/backlight/backlight.c
> +++ b/drivers/video/backlight/backlight.c
> @@ -292,10 +292,13 @@ static ssize_t actual_brightness_show(struct device *dev,
>  	struct backlight_device *bd = to_backlight_device(dev);
>  
>  	mutex_lock(&bd->ops_lock);
> -	if (bd->ops && bd->ops->get_brightness)
> -		rc = sprintf(buf, "%d\n", bd->ops->get_brightness(bd));
> -	else
> +	if (bd->ops && bd->ops->get_brightness) {
> +		rc = bd->ops->get_brightness(bd);
> +		if (rc >= 0)
> +			rc = sprintf(buf, "%d\n", rc);
> +	} else {
>  		rc = sprintf(buf, "%d\n", bd->props.brightness);
> +	}
>  	mutex_unlock(&bd->ops_lock);
>  
>  	return rc;
> @@ -381,9 +384,18 @@ ATTRIBUTE_GROUPS(bl_device);
>  void backlight_force_update(struct backlight_device *bd,
>  			    enum backlight_update_reason reason)
>  {
> +	int brightness;
> +
>  	mutex_lock(&bd->ops_lock);
> -	if (bd->ops && bd->ops->get_brightness)
> -		bd->props.brightness = bd->ops->get_brightness(bd);
> +	if (bd->ops && bd->ops->get_brightness) {
> +		brightness = bd->ops->get_brightness(bd);
> +		if (brightness >= 0)
> +			bd->props.brightness = brightness;
> +		else
> +			dev_warn(&bd->dev,
> +				 "Could not update brightness from device: errno = %d",
> +				 -brightness);

The format string is missing a \n and should it really be a dev_warn()?
Is dev_err() more appropriate?

Also please print the error symbolically (which is self explaining
meaning we don't need the errno prefix):

		"Could not update brightness from device: %pe\n",
		ERR_PTR(brightness)



Daniel.


> +	}
>  	mutex_unlock(&bd->ops_lock);
>  	backlight_generate_event(bd, reason);
>  }
> 
> base-commit: 79fad92f2e596f5a8dd085788a24f540263ef887
> -- 
> 2.33.0
>
diff mbox series

Patch

diff --git a/drivers/video/backlight/backlight.c b/drivers/video/backlight/backlight.c
index 537fe1b376ad..d681962f8509 100644
--- a/drivers/video/backlight/backlight.c
+++ b/drivers/video/backlight/backlight.c
@@ -292,10 +292,13 @@  static ssize_t actual_brightness_show(struct device *dev,
 	struct backlight_device *bd = to_backlight_device(dev);
 
 	mutex_lock(&bd->ops_lock);
-	if (bd->ops && bd->ops->get_brightness)
-		rc = sprintf(buf, "%d\n", bd->ops->get_brightness(bd));
-	else
+	if (bd->ops && bd->ops->get_brightness) {
+		rc = bd->ops->get_brightness(bd);
+		if (rc >= 0)
+			rc = sprintf(buf, "%d\n", rc);
+	} else {
 		rc = sprintf(buf, "%d\n", bd->props.brightness);
+	}
 	mutex_unlock(&bd->ops_lock);
 
 	return rc;
@@ -381,9 +384,18 @@  ATTRIBUTE_GROUPS(bl_device);
 void backlight_force_update(struct backlight_device *bd,
 			    enum backlight_update_reason reason)
 {
+	int brightness;
+
 	mutex_lock(&bd->ops_lock);
-	if (bd->ops && bd->ops->get_brightness)
-		bd->props.brightness = bd->ops->get_brightness(bd);
+	if (bd->ops && bd->ops->get_brightness) {
+		brightness = bd->ops->get_brightness(bd);
+		if (brightness >= 0)
+			bd->props.brightness = brightness;
+		else
+			dev_warn(&bd->dev,
+				 "Could not update brightness from device: errno = %d",
+				 -brightness);
+	}
 	mutex_unlock(&bd->ops_lock);
 	backlight_generate_event(bd, reason);
 }