hwmon/smsc47b397: Don't report missing fans as spinning at 82 RPM

Also protects ourselves against a possible division by zero.

Signed-off-by: Jean Delvare <khali@linux-fr.org>
Signed-off-by: Mark M. Hoffman <mhoffman@lightlink.com>

1 files changed, 2 insertions, 0 deletions

diff --git a/drivers/hwmon/smsc47b397.c b/drivers/hwmon/smsc47b397.c
index 3b65b0e61c4..45266b30ce1 100644
--- a/drivers/hwmon/smsc47b397.c
+++ b/drivers/hwmon/smsc47b397.c
@@ -174,6 +174,8 @@ static SENSOR_DEVICE_ATTR(temp4_input, S_IRUGO, show_temp, NULL, 3);
    REG: count of 90kHz pulses / revolution */
 static int fan_from_reg(u16 reg)
 {
+        if (reg == 0 || reg == 0xffff)
+                return 0;
         return 90000 * 60 / reg;
 }