net: phy: phy driver features are mandatory

Since phy driver features became a link_mode bitmap, phy drivers that
don't have a list of features configured will cause the kernel to crash
when probed.

Prevent the phy driver from registering if the features field is missing.

Fixes: 719655a1 ("net: phy: Replace phy driver features u32 with link_mode bitmap")
Reported-by: Scott Wood <oss@buserror.net>
Signed-off-by: Camelia Groza <camelia.groza@nxp.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

drivers/net/phy/phy_device.c

@@ -2255,6 +2255,11 @@ int phy_driver_register(struct phy_driver *new_driver, struct module *owner)
 {
 	int retval;
 
+	if (WARN_ON(!new_driver->features)) {
+		pr_err("%s: Driver features are missing\n", new_driver->name);
+		return -EINVAL;
+	}
+
 	new_driver->mdiodrv.flags |= MDIO_DEVICE_IS_PHY;
 	new_driver->mdiodrv.driver.name = new_driver->name;
 	new_driver->mdiodrv.driver.bus = &mdio_bus_type;

include/linux/phy.h

@@ -469,8 +469,8 @@ struct phy_device {
  *   only works for PHYs with IDs which match this field
  * name: The friendly name of this PHY type
  * phy_id_mask: Defines the important bits of the phy_id
- * features: A list of features (speed, duplex, etc) supported
- *   by this PHY
+ * features: A mandatory list of features (speed, duplex, etc)
+ *   supported by this PHY
  * flags: A bitfield defining certain other features this PHY
  *   supports (like interrupts)
  *