hwmon: (pmbus_core) Fix NULL pointer dereference

Pass i2c_client to _pmbus_is_enabled to drop the assumption
that a regulator device is passed in.

This will fix the issue of a NULL pointer dereference when called from
_pmbus_get_flags.

Fixes: df5f6b6 ("hwmon: (pmbus/core) Generalise pmbus get status")
Cc: stable@vger.kernel.org # v6.4
Signed-off-by: Patrick Rudolph <patrick.rudolph@9elements.com>
Signed-off-by: Naresh Solanki <Naresh.Solanki@9elements.com>
Link: https://lore.kernel.org/r/20230725125428.3966803-2-Naresh.Solanki@9elements.com
Signed-off-by: Guenter Roeck <linux@roeck-us.net>

Author: PatrickRudolph

drivers/hwmon/pmbus/pmbus_core.c

@@ -2745,9 +2745,8 @@ static const struct pmbus_status_category __maybe_unused pmbus_status_flag_map[]
 	},
 };
 
-static int _pmbus_is_enabled(struct device *dev, u8 page)
+static int _pmbus_is_enabled(struct i2c_client *client, u8 page)
 {
-	struct i2c_client *client = to_i2c_client(dev->parent);
 	int ret;
 
 	ret = _pmbus_read_byte_data(client, page, PMBUS_OPERATION);
@@ -2758,14 +2757,13 @@ static int _pmbus_is_enabled(struct device *dev, u8 page)
 	return !!(ret & PB_OPERATION_CONTROL_ON);
 }
 
-static int __maybe_unused pmbus_is_enabled(struct device *dev, u8 page)
+static int __maybe_unused pmbus_is_enabled(struct i2c_client *client, u8 page)
 {
-	struct i2c_client *client = to_i2c_client(dev->parent);
 	struct pmbus_data *data = i2c_get_clientdata(client);
 	int ret;
 
 	mutex_lock(&data->update_lock);
-	ret = _pmbus_is_enabled(dev, page);
+	ret = _pmbus_is_enabled(client, page);
 	mutex_unlock(&data->update_lock);
 
 	return ret;
@@ -2844,7 +2842,7 @@ static int _pmbus_get_flags(struct pmbus_data *data, u8 page, unsigned int *flag
 	if (status < 0)
 		return status;
 
-	if (_pmbus_is_enabled(dev, page)) {
+	if (_pmbus_is_enabled(client, page)) {
 		if (status & PB_STATUS_OFF) {
 			*flags |= REGULATOR_ERROR_FAIL;
 			*event |= REGULATOR_EVENT_FAIL;
@@ -2898,7 +2896,10 @@ static int __maybe_unused pmbus_get_flags(struct pmbus_data *data, u8 page, unsi
 #if IS_ENABLED(CONFIG_REGULATOR)
 static int pmbus_regulator_is_enabled(struct regulator_dev *rdev)
 {
-	return pmbus_is_enabled(rdev_get_dev(rdev), rdev_get_id(rdev));
+	struct device *dev = rdev_get_dev(rdev);
+	struct i2c_client *client = to_i2c_client(dev->parent);
+
+	return pmbus_is_enabled(client, rdev_get_id(rdev));
 }
 
 static int _pmbus_regulator_on_off(struct regulator_dev *rdev, bool enable)