[PATCH v4] backlight: pwm_bl: Fix uninitialized variable

[Daniel Thompson <daniel.thompson@linaro.org>]

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 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>
Reviewed-by: Douglas Anderson <dianders@chromium.org>
Acked-by: Lee Jones <lee.jones@linaro.org>
---

Notes:
    v4:
     - Remove line break from Fixes: and update the *-by:s
    
    v3:
     - 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).
    
    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 | 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;
--
2.17.1