i2c/tsl2550: Fix lux value in dark environment

commit 96f699ad09c8b3c55cd229506a9add0047838e3e upstream.

I've tested TSL2550 driver and I've found a bug: when light is off,
returned value from tsl2550_calculate_lux function is -1 when it should
be 0 (sensor correctly read that light was off).

I think the bug is that a zero c0 value (approximated value of ch0) is
misinterpreted as an error.

Signed-off-by: Michele Jr De Candia <michele.decandia@valueteam.com>
Acked-by: Rodolfo Giometti <giometti@linux.it>
Signed-off-by: Jean Delvare <khali@linux-fr.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>

diff --git a/drivers/i2c/chips/tsl2550.c b/drivers/i2c/chips/tsl2550.c
index 1a9cc13..b96f302 100644 (file)
--- a/drivers/i2c/chips/tsl2550.c
+++ b/drivers/i2c/chips/tsl2550.c
@@ -27,7 +27,7 @@
 #include <linux/delay.h>
 
 #define TSL2550_DRV_NAME       "tsl2550"
-#define DRIVER_VERSION         "1.1.1"
+#define DRIVER_VERSION         "1.1.2"
 
 /*
  * Defines
@@ -189,13 +189,16 @@ static int tsl2550_calculate_lux(u8 ch0, u8 ch1)
        u8 r = 128;
 
        /* Avoid division by 0 and count 1 cannot be greater than count 0 */
-       if (c0 && (c1 <= c0))
-               r = c1 * 128 / c0;
+       if (c1 <= c0)
+               if (c0) {
+                       r = c1 * 128 / c0;
+
+                       /* Calculate LUX */
+                       lux = ((c0 - c1) * ratio_lut[r]) / 256;
+               } else
+                       lux = 0;
        else
-               return -1;
-
-       /* Calculate LUX */
-       lux = ((c0 - c1) * ratio_lut[r]) / 256;
+               return -EAGAIN;
 
        /* LUX range check */
        return lux > TSL2550_MAX_LUX ? TSL2550_MAX_LUX : lux;