net: move 6lowpan compression code to separate module

IEEE 802.15.4 and Bluetooth networking stacks share 6lowpan compression
code. Instead of introducing Makefile/Kconfig hacks, build this code as
a separate module referenced from both ieee802154 and bluetooth modules.

This fixes the following build error observed in some kernel
configurations:

net/built-in.o: In function `header_create': 6lowpan.c:(.text+0x166149): undefined reference to `lowpan_header_compress'
net/built-in.o: In function `bt_6lowpan_recv': (.text+0x166b3c): undefined reference to `lowpan_process_data'

Reported-by: Randy Dunlap <rdunlap@infradead.org>
Signed-off-by: Dmitry Eremin-Solenikov <dmitry_eremin@mentor.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

2 files changed, 9 insertions, 1 deletions

diff --git a/net/ieee802154/Kconfig b/net/ieee802154/Kconfig
index b2e06df0076c..9c9879d5ea64 100644
--- a/net/ieee802154/Kconfig
+++ b/net/ieee802154/Kconfig
@@ -13,5 +13,12 @@ config IEEE802154
 config IEEE802154_6LOWPAN
         tristate "6lowpan support over IEEE 802.15.4"
         depends on IEEE802154 && IPV6
+        select 6LOWPAN_IPHC
         ---help---
         IPv6 compression over IEEE 802.15.4.
+
+config 6LOWPAN_IPHC
+        tristate
+        ---help---
+          6lowpan compression code which is shared between IEEE 802.15.4 and Bluetooth
+          stacks.
diff --git a/net/ieee802154/Makefile b/net/ieee802154/Makefile
index 951a83ee8af4..e8f05885ced6 100644
--- a/net/ieee802154/Makefile
+++ b/net/ieee802154/Makefile
@@ -1,5 +1,6 @@
 obj-$(CONFIG_IEEE802154) += ieee802154.o af_802154.o
-obj-$(CONFIG_IEEE802154_6LOWPAN) += 6lowpan.o 6lowpan_iphc.o
+obj-$(CONFIG_IEEE802154_6LOWPAN) += 6lowpan.o
+obj-$(CONFIG_6LOWPAN_IPHC) += 6lowpan_iphc.o
 
 ieee802154-y := netlink.o nl-mac.o nl-phy.o nl_policy.o wpan-class.o
 af_802154-y := af_ieee802154.o raw.o dgram.o