linux-kernel - [PATCH v3] backlight: pwm_bl: Fix uninitialized variable

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Message-Id: <20180724071223.18901-1-daniel.thompson@linaro.org>
Date:   Tue, 24 Jul 2018 08:12:23 +0100
From:   Daniel Thompson <daniel.thompson@...aro.org>
To:     Lee Jones <lee.jones@...aro.org>,
        Daniel Thompson <daniel.thompson@...aro.org>,
        Jingoo Han <jingoohan1@...il.com>
Cc:     Thierry Reding <thierry.reding@...il.com>,
        Bartlomiej Zolnierkiewicz <b.zolnierkie@...sung.com>,
        Marcel Ziswiler <marcel.ziswiler@...adex.com>,
        linux-pwm@...r.kernel.org, dri-devel@...ts.freedesktop.org,
        linux-fbdev@...r.kernel.org, linux-kernel@...r.kernel.org,
        patches@...aro.org
Subject: [PATCH v3] backlight: pwm_bl: Fix uninitialized variable

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@...adex.com>
Signed-off-by: Daniel Thompson <daniel.thompson@...aro.org>
Tested-by: Marcel Ziswiler <marcel.ziswiler@...adex.com>
---

Notes:
    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