linux-kernel - [PATCH] backlight: adp88x0: fix uninitialized variable use

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Date:	Mon, 23 Nov 2015 14:44:13 +0100
From:	Arnd Bergmann <arnd@...db.de>
To:	Jingoo Han <jingoohan1@...il.com>, Lee Jones <lee.jones@...aro.org>
Cc:	Michael Hennerich <michael.hennerich@...log.com>,
	Jean-Christophe Plagniol-Villard <plagnioj@...osoft.com>,
	Tomi Valkeinen <tomi.valkeinen@...com>,
	linux-fbdev@...r.kernel.org, linux-kernel@...r.kernel.org,
	linux-arm-kernel@...ts.infradead.org
Subject: [PATCH] backlight: adp88x0: fix uninitialized variable use

gcc correctly warns about both the adp8860 and adp8870 backlight
drivers using an uninitialized variable in their error handling
path:

drivers/video/backlight/adp8870_bl.c: In function 'adp8870_bl_ambient_light_zone_store':
drivers/video/backlight/adp8870_bl.c:811:11: warning: 'reg_val' may be used uninitialized in this function

This changes the code to only write back the data if it was
correctly read to start with.

As a side-note, the drivers are mostly identical, so I think they
should really be merged into one file to avoid having to fix every
bug twice.

Signed-off-by: Arnd Bergmann <arnd@...db.de>

diff --git a/drivers/video/backlight/adp8860_bl.c b/drivers/video/backlight/adp8860_bl.c
index 98ffe71e8af2..f0d4c0324580 100644
--- a/drivers/video/backlight/adp8860_bl.c
+++ b/drivers/video/backlight/adp8860_bl.c
@@ -621,10 +621,12 @@ static ssize_t adp8860_bl_ambient_light_zone_store(struct device *dev,
 
 		/* Set user supplied ambient light zone */
 		mutex_lock(&data->lock);
-		adp8860_read(data->client, ADP8860_CFGR, &reg_val);
-		reg_val &= ~(CFGR_BLV_MASK << CFGR_BLV_SHIFT);
-		reg_val |= (val - 1) << CFGR_BLV_SHIFT;
-		adp8860_write(data->client, ADP8860_CFGR, reg_val);
+		ret = adp8860_read(data->client, ADP8860_CFGR, &reg_val);
+		if (!ret) {
+			reg_val &= ~(CFGR_BLV_MASK << CFGR_BLV_SHIFT);
+			reg_val |= (val - 1) << CFGR_BLV_SHIFT;
+			adp8860_write(data->client, ADP8860_CFGR, reg_val);
+		}
 		mutex_unlock(&data->lock);
 	}
 
diff --git a/drivers/video/backlight/adp8870_bl.c b/drivers/video/backlight/adp8870_bl.c
index 9d738352d7d4..21acac90fd77 100644
--- a/drivers/video/backlight/adp8870_bl.c
+++ b/drivers/video/backlight/adp8870_bl.c
@@ -807,10 +807,12 @@ static ssize_t adp8870_bl_ambient_light_zone_store(struct device *dev,
 
 		/* Set user supplied ambient light zone */
 		mutex_lock(&data->lock);
-		adp8870_read(data->client, ADP8870_CFGR, &reg_val);
-		reg_val &= ~(CFGR_BLV_MASK << CFGR_BLV_SHIFT);
-		reg_val |= (val - 1) << CFGR_BLV_SHIFT;
-		adp8870_write(data->client, ADP8870_CFGR, reg_val);
+		ret = adp8870_read(data->client, ADP8870_CFGR, &reg_val);
+		if (!ret) {
+			reg_val &= ~(CFGR_BLV_MASK << CFGR_BLV_SHIFT);
+			reg_val |= (val - 1) << CFGR_BLV_SHIFT;
+			adp8870_write(data->client, ADP8870_CFGR, reg_val);
+		}
 		mutex_unlock(&data->lock);
 	}
 

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