net: ethtool: netlink: introduce ethnl_update_bool()

Due to the fact that the kernel-side data structures have been carried
over from the ioctl-based ethtool, we are now in the situation where we
have an ethnl_update_bool32() function, but the plain function that
operates on a boolean value kept in an actual u8 netlink attribute
doesn't exist.

With new ethtool features that are exposed solely over netlink, the
kernel data structures will use the "bool" type, so we will need this
kind of helper. Introduce it now; it's needed for things like
verify-disabled for the MAC merge configuration.
Signed-off-by: Vladimir Oltean <vladimir.oltean@nxp.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

net/ethtool/netlink.h

@@ -111,6 +111,32 @@ static inline void ethnl_update_u8(u8 *dst, const struct nlattr *attr,
 	*mod = true;
 }
 
+/**
+ * ethnl_update_bool() - update bool from NLA_U8 attribute
+ * @dst:  value to update
+ * @attr: netlink attribute with new value or null
+ * @mod:  pointer to bool for modification tracking
+ *
+ * Use the u8 value from NLA_U8 netlink attribute @attr to set bool variable
+ * pointed to by @dst to false (if zero) or 1 (if not); do nothing if @attr is
+ * null. Bool pointed to by @mod is set to true if this function changed the
+ * logical value of *dst, otherwise it is left as is.
+ */
+static inline void ethnl_update_bool(bool *dst, const struct nlattr *attr,
+				     bool *mod)
+{
+	u8 val;
+
+	if (!attr)
+		return;
+	val = !!nla_get_u8(attr);
+	if (*dst == val)
+		return;
+
+	*dst = val;
+	*mod = true;
+}
+
 /**
  * ethnl_update_bool32() - update u32 used as bool from NLA_U8 attribute
  * @dst:  value to update