From 832f9fec6a0c0d0e37a1610f267b4ffdd8c8895e Mon Sep 17 00:00:00 2001 From: "iw3gtf@arcor.de" Date: Thu, 14 Jul 2016 16:17:18 +0200 Subject: video/backlight-pwm: properly handle the case of an empty 'brightness-levels' in the device tree. In case of an empty 'brightness-levels' array in the device tree or a non empty one but containing only zeros the value of 'pwm_backlight->scale' would remain 0 possibly causing a division by zero in the function compute_duty_cycle(). To fix it we check the computed value in case we actually have a 'brightness-levels' array in the device tree otherwise we implicitly assume a simple array of the form { 0, 1, 2, ..., 100 } and set the scale to 100. Signed-off-by: Sascha Hauer --- drivers/video/backlight-pwm.c | 20 +++++++++++++------- 1 file changed, 13 insertions(+), 7 deletions(-) diff --git a/drivers/video/backlight-pwm.c b/drivers/video/backlight-pwm.c index 5ff40a94c3..7f1715ddde 100644 --- a/drivers/video/backlight-pwm.c +++ b/drivers/video/backlight-pwm.c @@ -128,6 +128,13 @@ static int pwm_backlight_parse_dt(struct device_d *dev, if (!node) return -ENODEV; + ret = of_property_read_u32(node, "default-brightness-level", + &value); + if (ret < 0) + return ret; + + pwm_backlight->backlight.brightness_default = value; + /* determine the number of brightness levels */ prop = of_find_property(node, "brightness-levels", &length); if (!prop) @@ -153,14 +160,13 @@ static int pwm_backlight_parse_dt(struct device_d *dev, if (pwm_backlight->levels[i] > pwm_backlight->scale) pwm_backlight->scale = pwm_backlight->levels[i]; - ret = of_property_read_u32(node, "default-brightness-level", - &value); - if (ret < 0) - return ret; - - pwm_backlight->backlight.brightness_default = value; - pwm_backlight->backlight.brightness_max = pwm_backlight->scale; + if (pwm_backlight->scale == 0) + return -EINVAL; + } else { + /* We implicitly assume here a linear levels array { 0, 1, 2, ... 100 } */ + pwm_backlight->scale = 100; } + pwm_backlight->backlight.brightness_max = pwm_backlight->scale; pwm_backlight->enable_gpio = of_get_named_gpio_flags(node, "enable-gpios", 0, &flags); -- cgit v1.2.3