[patch 03/28] i2c/tsl2550: Fix lux value in dark environment

Greg KH
2009-08-13T19:47:44Z

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2.6.27-stable review patch. If anyone has any objections, please let us know.

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From: Michele Jr De Candia <michele.decandia@valueteam.com>

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>

---
drivers/i2c/chips/tsl2550.c | 17 ++++++++++-------
1 file changed, 10 insertions(+), 7 deletions(-)

--- 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 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;