ieee802154: Convert scan error messages to extack

Instead of printing error messages in the kernel log, let's use extack.
When there is a netlink error returned that could be further specified
with a string, use extack as well.

Apply this logic to the very recent scan/beacon infrastructure.

Fixes: ed3557c ("ieee802154: Add support for user scanning requests")
Fixes: 9bc1145 ("ieee802154: Add support for user beaconing requests")
Suggested-by: Jakub Kicinski <kuba@kernel.org>
Signed-off-by: Miquel Raynal <miquel.raynal@bootlin.com>
Link: https://lore.kernel.org/r/20230214135035.1202471-3-miquel.raynal@bootlin.com
Signed-off-by: Stefan Schmidt <stefan@datenfreihafen.org>

net/ieee802154/nl802154.c

@@ -1407,9 +1407,15 @@ static int nl802154_trigger_scan(struct sk_buff *skb, struct genl_info *info)
 	u8 type;
 	int err;
 
-	/* Monitors are not allowed to perform scans */
-	if (wpan_dev->iftype == NL802154_IFTYPE_MONITOR)
+	if (wpan_dev->iftype == NL802154_IFTYPE_MONITOR) {
+		NL_SET_ERR_MSG(info->extack, "Monitors are not allowed to perform scans");
 		return -EPERM;
+	}
+
+	if (!nla_get_u8(info->attrs[NL802154_ATTR_SCAN_TYPE])) {
+		NL_SET_ERR_MSG(info->extack, "Malformed request, missing scan type");
+		return -EINVAL;
+	}
 
 	request = kzalloc(sizeof(*request), GFP_KERNEL);
 	if (!request)
@@ -1424,7 +1430,7 @@ static int nl802154_trigger_scan(struct sk_buff *skb, struct genl_info *info)
 		request->type = type;
 		break;
 	default:
-		pr_err("Unsupported scan type: %d\n", type);
+		NL_SET_ERR_MSG_FMT(info->extack, "Unsupported scan type: %d", type);
 		err = -EINVAL;
 		goto free_request;
 	}
@@ -1576,12 +1582,13 @@ nl802154_send_beacons(struct sk_buff *skb, struct genl_info *info)
 	struct cfg802154_beacon_request *request;
 	int err;
 
-	/* Only coordinators can send beacons */
-	if (wpan_dev->iftype != NL802154_IFTYPE_COORD)
+	if (wpan_dev->iftype != NL802154_IFTYPE_COORD) {
+		NL_SET_ERR_MSG(info->extack, "Only coordinators can send beacons");
 		return -EOPNOTSUPP;
+	}
 
 	if (wpan_dev->pan_id == cpu_to_le16(IEEE802154_PANID_BROADCAST)) {
-		pr_err("Device is not part of any PAN\n");
+		NL_SET_ERR_MSG(info->extack, "Device is not part of any PAN");
 		return -EPERM;
 	}