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Subject[PATCH v2] backlight: pwm_bl: Fix uninitialized variable
Date
Currently, if the DT does not define num-interpolated-steps then
num_steps is undefined and the interpolation code will deploy randomly.
Fix this.

Additionally fix a small grammar error that was identified and
tighten up return code checking of DT properties, both of which came
up during review of this patch.

Fixes: 573fe6d1c25c ("backlight: pwm_bl: Linear interpolation between
brightness-levels")
Reported-by: Marcel Ziswiler <marcel.ziswiler@toradex.com>
Signed-off-by: Daniel Thompson <daniel.thompson@linaro.org>
Tested-by: Marcel Ziswiler <marcel.ziswiler@toradex.com>
---

Notes:
v2:
- Simplify SoB chain (with Marcel's permission)
- Separate complex if statement and make other similar calls use same
return code checking approach
- Tidy up comment formatting and fix pre-existing grammar error

drivers/video/backlight/pwm_bl.c | 25 ++++++++++++-------------
1 file changed, 12 insertions(+), 13 deletions(-)

diff --git a/drivers/video/backlight/pwm_bl.c b/drivers/video/backlight/pwm_bl.c
index 9ee4c1b735b2..f7799f62fea0 100644
--- a/drivers/video/backlight/pwm_bl.c
+++ b/drivers/video/backlight/pwm_bl.c
@@ -284,30 +284,29 @@ static int pwm_backlight_parse_dt(struct device *dev,
ret = of_property_read_u32_array(node, "brightness-levels",
data->levels,
data->max_brightness);
- if (ret < 0)
+ if (!ret)
return ret;

ret = of_property_read_u32(node, "default-brightness-level",
&value);
- if (ret < 0)
+ if (!ret)
return ret;

data->dft_brightness = value;

/*
* This property is optional, if is set enables linear
- * interpolation between each of the values of brightness levels
- * and creates a new pre-computed table.
+ * interpolation between each of the values of brightness
+ * levels and creates a new pre-computed table.
*/
- of_property_read_u32(node, "num-interpolated-steps",
- &num_steps);
-
- /*
- * Make sure that there is at least two entries in the
- * brightness-levels table, otherwise we can't interpolate
- * between two points.
- */
- if (num_steps) {
+ ret = of_property_read_u32(node, "num-interpolated-steps",
+ &num_steps);
+ if (!ret || num_steps) {
+ /*
+ * Make sure that there are at least two entries in
+ * the brightness-levels table, otherwise we can't
+ * interpolate between two points.
+ */
if (data->max_brightness < 2) {
dev_err(dev, "can't interpolate\n");
return -EINVAL;
--
2.17.1
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