[PATCH AUTOSEL 5.15 03/65] backlight: Propagate errors from get_brightness()

[Sasha Levin <sashal@kernel.org>]

From: Thomas Weißschuh <linux@weissschuh.net>

[ Upstream commit 563edf85ce18a90dd0a7b39e279a691d937205f6 ]

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>
Reviewed-by: Daniel Thompson <daniel.thompson@linaro.org>
Signed-off-by: Lee Jones <lee.jones@linaro.org>
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
 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 537fe1b376ad7..4658cfb75aa28 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_err(&bd->dev,
+				"Could not update brightness from device: %pe\n",
+				ERR_PTR(brightness));
+	}
 	mutex_unlock(&bd->ops_lock);
 	backlight_generate_event(bd, reason);
 }
-- 
2.33.0