There are several problems in the way the hysteresis value is handled by the lm90 driver: * In show_temphyst(), specific handling of the MAX6646 is missing, so the hysteresis is reported incorrectly if the critical temperature is over 127 degrees C. * In set_temphyst(), the new hysteresis register value is written to the chip but data->temp_hyst isn't updated accordingly, so there is a short period of time (up to 2 seconds) where the old hystereris value will be returned while the new one is already active. * In set_temphyst(), the critical temperature which is used as a base to compute the value of the hysteresis register lacks device-specific handling. As a result, the value of the hysteresis register might be incorrect for the ADT7461 and MAX6646 chips. Fix these 3 bugs. Signed-off-by: Jean Delvare <khali at linux-fr.org> Cc: Ben Hutchings <bhutchings at solarflare.com> Cc: Nate Case <ncase at xes-inc.com> --- Ben, Nate, can you please review and test this patch? drivers/hwmon/lm90.c | 15 ++++++++++++--- 1 file changed, 12 insertions(+), 3 deletions(-) --- linux-2.6.28-rc0.orig/drivers/hwmon/lm90.c 2008-10-20 13:53:08.000000000 +0200 +++ linux-2.6.28-rc0/drivers/hwmon/lm90.c 2008-10-20 13:58:48.000000000 +0200 @@ -461,6 +461,8 @@ static ssize_t show_temphyst(struct devi if (data->kind == adt7461) temp = temp_from_u8_adt7461(data, data->temp8[attr->index]); + else if (data->kind == max6646) + temp = temp_from_u8(data->temp8[attr->index]); else temp = temp_from_s8(data->temp8[attr->index]); @@ -473,12 +475,19 @@ static ssize_t set_temphyst(struct devic struct i2c_client *client = to_i2c_client(dev); struct lm90_data *data = i2c_get_clientdata(client); long val = simple_strtol(buf, NULL, 10); - long hyst; + int temp; mutex_lock(&data->update_lock); - hyst = temp_from_s8(data->temp8[2]) - val; + if (data->kind == adt7461) + temp = temp_from_u8_adt7461(data, data->temp8[2]); + else if (data->kind == max6646) + temp = temp_from_u8(data->temp8[2]); + else + temp = temp_from_s8(data->temp8[2]); + + data->temp_hyst = hyst_to_reg(temp - val); i2c_smbus_write_byte_data(client, LM90_REG_W_TCRIT_HYST, - hyst_to_reg(hyst)); + data->temp_hyst); mutex_unlock(&data->update_lock); return count; } -- Jean Delvare
