backlight: lp855x: Catch errors when changing brightness

The lp855x_bl_update_status function's return type is int, but
it always returns 0, without checking for the results of the
write_byte/pwm_ctrl functions called within.

Make this function return the return values of the functions it
calls, and modify the lp855x_pwm_ctrl function to return errors.

Signed-off-by: Artur Weber <aweber.kernel@gmail.com>
Reviewed-by: Daniel Thompson <daniel.thompson@linaro.org>
Link: https://lore.kernel.org/r/20230714121440.7717-3-aweber.kernel@gmail.com
Signed-off-by: Lee Jones <lee@kernel.org>

drivers/video/backlight/lp855x_bl.c

@@ -217,7 +217,7 @@ static int lp855x_configure(struct lp855x *lp)
 	return ret;
 }
 
-static void lp855x_pwm_ctrl(struct lp855x *lp, int br, int max_br)
+static int lp855x_pwm_ctrl(struct lp855x *lp, int br, int max_br)
 {
 	struct pwm_state state;
 
@@ -234,23 +234,26 @@ static void lp855x_pwm_ctrl(struct lp855x *lp, int br, int max_br)
 	state.duty_cycle = div_u64(br * state.period, max_br);
 	state.enabled = state.duty_cycle;
 
-	pwm_apply_state(lp->pwm, &state);
+	return pwm_apply_state(lp->pwm, &state);
 }
 
 static int lp855x_bl_update_status(struct backlight_device *bl)
 {
 	struct lp855x *lp = bl_get_data(bl);
 	int brightness = bl->props.brightness;
+	int ret;
 
 	if (bl->props.state & (BL_CORE_SUSPENDED | BL_CORE_FBBLANK))
 		brightness = 0;
 
 	if (lp->mode == PWM_BASED)
-		lp855x_pwm_ctrl(lp, brightness, bl->props.max_brightness);
+		ret = lp855x_pwm_ctrl(lp, brightness,
+				      bl->props.max_brightness);
 	else if (lp->mode == REGISTER_BASED)
-		lp855x_write_byte(lp, lp->cfg->reg_brightness, (u8)brightness);
+		ret = lp855x_write_byte(lp, lp->cfg->reg_brightness,
+					(u8)brightness);
 
-	return 0;
+	return ret;
 }
 
 static const struct backlight_ops lp855x_bl_ops = {