[patch 10/47] w1: w1 temp calculation overflow fix

Greg KH
2009-02-14T01:05:04Z

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

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From: Ian Dall <ian@beware.dropbear.id.au>

commit 507e2fbaaacb6f164b4125b87c5002f95143174b upstream.

Addresses http://bugzilla.kernel.org/show_bug.cgi?id=12646

When the temperature exceeds 32767 milli-degrees the temperature overflows
to -32768 millidegrees. These are bothe well within the -55 - +125 degree
range for the sensor.

Fix overflow in left-shift of a u8.

Signed-off-by: Ian Dall <ian@beware.dropbear.id.au>
Signed-off-by: Evgeniy Polyakov <zbr@ioremap.net>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>

---
drivers/w1/slaves/w1_therm.c | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)

--- a/drivers/w1/slaves/w1_therm.c
+++ b/drivers/w1/slaves/w1_therm.c
@@ -113,7 +113,7 @@ static struct w1_therm_family_converter

static inline int w1_DS18B20_convert_temp(u8 rom[9])
{
- s16 t = (rom[1] << 8) | rom[0];
+ int t = ((s16)rom[1] << 8) | rom[0];
t = t*1000/16;
return t;
}