Re: [PATCH] TSL2550 driver bugfix

[Jonathan Cameron <jic23-KWPb1pKIrIJaa/9Udqfwiw@public.gmane.org>]

Michele De Candia (VT) wrote:
> Hi all,
> 
> 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.
> I'm attaching you a patch that fixes the bug.
> 
> Regards,
> Michele Jr De Candia
Sounds reasonable, but I think a stray line got away in your patch (see below)
Not to mention, if the c1 <= c0 check is still valid, should you not also
confirm that c1 == 0 as well? Perhaps reverse the ordering?
if (c1 <= c0)
	if(c0) {
		r = c1* 128 / c0;
		lux = ((c0 - c1) * ratio_lut[r]) / 256;
	} else
		lux = 0;
else
	return -1;
	

Signed-off-by: Michele Jr De Candia <michele.decandia-EZxuzQJkuwwybS5Ee8rs3A@public.gmane.org>

diff --git a/drivers/i2c/chips/tsl2550.c b/drivers/i2c/chips/tsl2550.c
index 1a9cc13..6bad072 100644
--- a/drivers/i2c/chips/tsl2550.c
+++ b/drivers/i2c/chips/tsl2550.c
@@ -189,10 +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;
-	else
-		return -1;
+	if (c0)	{
+		if (c1 <= c0)
+			r = c1 * 128 / c0;
+		else
+			return -1;
+			
+		/* Calculate LUX */
+		lux = ((c0 - c1) * ratio_lut[r]) / 256;
+	}
+	else lux = 0;
 

This last line should have been removed I think?
 	/* Calculate LUX */
	lux = ((c0 - c1) * ratio_lut[r]) / 256;

---
Jonathan Cameron