When the LM75 temperature sensor measures a temperature below 0 C, the current driver does not perform sign extension, so the result returned is 256 C too high. This patch fixes the problem.
Signed-off-by: Larry Johnson lrj@acm.org --- The patch was tested on the AMCC Sequoia board, which uses the AD7414 temperature sensor. It appears that other drivers, such as "ds1621.c", may have the same bug, but I have no way of testing these.
drivers/hwmon/lm75.c | 8 +++++++- 1 files changed, 7 insertions(+), 1 deletions(-)
diff --git a/drivers/hwmon/lm75.c b/drivers/hwmon/lm75.c index 63f3b75..e29b294 100644 --- a/drivers/hwmon/lm75.c +++ b/drivers/hwmon/lm75.c @@ -179,7 +179,13 @@ int dtt_init (void)
int dtt_get_temp(int sensor) { - return (dtt_read(sensor, DTT_READ_TEMP) / 256); + int const ret = dtt_read(sensor, DTT_READ_TEMP); + + if (ret < 0) { + printf("DTT temperature read failed.\n"); + return 0; + } + return (int)((int16_t) ret / 256); } /* dtt_get_temp() */
#endif /* CONFIG_DTT_LM75 */