[PATCH v3] backlight: pwm_bl: Fix uninitialized variable

From: Daniel Thompson
Date: Tue Jul 24 2018 - 03:12:47 EST

Currently, if the DT does not define num-interpolated-steps then
num_steps is undefined and the interpolation code will deploy randomly.
Fix with a simple initialize to zero.

Fixes: 573fe6d1c25c ("backlight: pwm_bl: Linear interpolation between
Reported-by: Marcel Ziswiler <marcel.ziswiler@xxxxxxxxxxx>
Signed-off-by: Daniel Thompson <daniel.thompson@xxxxxxxxxx>
Tested-by: Marcel Ziswiler <marcel.ziswiler@xxxxxxxxxxx>

- Switch to the simplest fix and zero the uninitialized variable. git
grep indicates that ~25% of calls to of_property_read_u32() use this
pattern (pre-initialize optional properties with sane values and
ignore the return code).

- 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 | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/drivers/video/backlight/pwm_bl.c b/drivers/video/backlight/pwm_bl.c
index 9ee4c1b735b2..bdfcc0a71db1 100644
--- a/drivers/video/backlight/pwm_bl.c
+++ b/drivers/video/backlight/pwm_bl.c
@@ -250,7 +250,7 @@ static int pwm_backlight_parse_dt(struct device *dev,
struct device_node *node = dev->of_node;
unsigned int num_levels = 0;
unsigned int levels_count;
- unsigned int num_steps;
+ unsigned int num_steps = 0;
struct property *prop;
unsigned int *table;
int length;