ieee802154: Introduce a helper to validate a channel

This helper for now only checks if the page member and channel member
are valid (in the specification range) and supported (by checking the
device capabilities). Soon two new parameters will be introduced and
having this helper will let us only modify its content rather than
modifying the logic everywhere else in the subsystem.

There is not functional change.

Signed-off-by: Miquel Raynal <miquel.raynal@bootlin.com>
Acked-by: Alexander Aring <aahringo@redhat.com>
Link: https://lore.kernel.org/r/20230103165644.432209-4-miquel.raynal@bootlin.com
Signed-off-by: Stefan Schmidt <stefan@datenfreihafen.org>

include/net/cfg802154.h

@@ -246,6 +246,17 @@ static inline void wpan_phy_net_set(struct wpan_phy *wpan_phy, struct net *net)
 	write_pnet(&wpan_phy->_net, net);
 }
 
+static inline bool ieee802154_chan_is_valid(struct wpan_phy *phy,
+					    u8 page, u8 channel)
+{
+	if (page > IEEE802154_MAX_PAGE ||
+	    channel > IEEE802154_MAX_CHANNEL ||
+	    !(phy->supported.channels[page] & BIT(channel)))
+		return false;
+
+	return true;
+}
+
 /**
  * struct ieee802154_addr - IEEE802.15.4 device address
  * @mode: Address mode from frame header. Can be one of:

net/ieee802154/nl802154.c

@@ -976,8 +976,7 @@ static int nl802154_set_channel(struct sk_buff *skb, struct genl_info *info)
 	channel = nla_get_u8(info->attrs[NL802154_ATTR_CHANNEL]);
 
 	/* check 802.15.4 constraints */
-	if (page > IEEE802154_MAX_PAGE || channel > IEEE802154_MAX_CHANNEL ||
-	    !(rdev->wpan_phy.supported.channels[page] & BIT(channel)))
+	if (!ieee802154_chan_is_valid(&rdev->wpan_phy, page, channel))
 		return -EINVAL;
 
 	return rdev_set_channel(rdev, page, channel);