Some PMBus chips do not support the VOUT_MODE register. To make matters worse, such chips may not return an error when reading the register either, but instead return 0xff. Check if the register exists using pmbus_check_byte_register() before reading its value. In addition, validate the returned value and ignore it if it is 0xff (which is invalid). Reported-by: Greg Schnorr <gschnorr@xxxxxxxxx> Signed-off-by: Guenter Roeck <guenter.roeck@xxxxxxxxxxxx> --- drivers/hwmon/pmbus_core.c | 7 ++++--- 1 files changed, 4 insertions(+), 3 deletions(-) diff --git a/drivers/hwmon/pmbus_core.c b/drivers/hwmon/pmbus_core.c index 0edab1c..b7c64ba 100644 --- a/drivers/hwmon/pmbus_core.c +++ b/drivers/hwmon/pmbus_core.c @@ -1426,10 +1426,11 @@ static void pmbus_find_attributes(struct i2c_client *client, static int pmbus_identify_common(struct i2c_client *client, struct pmbus_data *data) { - int vout_mode, exponent; + int vout_mode = -1, exponent; - vout_mode = pmbus_read_byte_data(client, 0, PMBUS_VOUT_MODE); - if (vout_mode >= 0) { + if (pmbus_check_byte_register(client, 0, PMBUS_VOUT_MODE)) + vout_mode = pmbus_read_byte_data(client, 0, PMBUS_VOUT_MODE); + if (vout_mode >= 0 && vout_mode != 0xff) { /* * Not all chips support the VOUT_MODE command, * so a failure to read it is not an error. -- 1.7.3.1 -- To unsubscribe from this list: send the line "unsubscribe linux-doc" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html