Index: head/sys/conf/config.mk
===================================================================
--- head/sys/conf/config.mk
+++ head/sys/conf/config.mk
@@ -0,0 +1,54 @@
+# $FreeBSD$
+#
+# Common code to marry kernel config(8) goo and module building goo.
+#
+
+# Generate options files that otherwise would be built
+# in substantially similar ways through the tree. Move
+# the code here when they all produce identical results
+# (or should)
+.if !defined(KERNBUILDDIR)
+opt_bpf.h:
+	echo "#define DEV_BPF 1" > ${.TARGET}
+.if ${MK_INET_SUPPORT} != "no"
+opt_inet.h:
+	@echo "#define INET 1" > ${.TARGET}
+	@echo "#define TCP_OFFLOAD 1" >> ${.TARGET}
+.endif
+.if ${MK_INET6_SUPPORT} != "no"
+opt_inet6.h:
+	@echo "#define INET6 1" > ${.TARGET}
+.endif
+.if ${MK_EISA} != "no"
+opt_eisa.h:
+	@echo "#define DEV_EISA 1" > ${.TARGET}
+.endif
+opt_mrouting.h:
+	echo "#define MROUTING 1" > ${.TARGET}
+opt_natm.h:
+	echo "#define NATM 1" > ${.TARGET}
+opt_scsi.h:
+	echo "#define SCSI_DELAY 15000" > ${.TARGET}
+opt_wlan.h:
+	echo "#define IEEE80211_DEBUG 1" > ${.TARGET}
+	echo "#define IEEE80211_AMPDU_AGE 1" >> ${.TARGET}
+	echo "#define IEEE80211_SUPPORT_MESH 1" >> ${.TARGET}
+KERN_OPTS.i386=NEW_PCIB DEV_PCI
+KERN_OPTS.pc98=NEW_PCIB DEV_PCI
+KERN_OPTS.amd64=NEW_PCIB DEV_PCI
+KERN_OPTS.powerpc=NEW_PCIB DEV_PCI
+KERN_OPTS=MROUTING NATM IEEE80211_DEBUG \
+	IEEE80211_AMPDU_AGE IEEE80211_SUPPORT_MESH DEV_BPF \
+	${KERN_OPTS.${MACHINE}} ${KERN_OPTS_EXTRA}
+.if ${MK_INET_SUPPORT} != "no"
+KERN_OPTS+= INET TCP_OFFLOAD
+.endif
+.if ${MK_INET6_SUPPORT} != "no"
+KERN_OPTS+= INET6
+.endif
+.if ${MK_EISA} != "no"
+KERN_OPTS+= DEV_EISA
+.endif
+.else
+KERN_OPTS!=cat ${KERNBUILDDIR}/opt*.h | awk '{print $$2;}' | sort -u
+.endif
Index: head/sys/conf/kmod.mk
===================================================================
--- head/sys/conf/kmod.mk
+++ head/sys/conf/kmod.mk
@@ -70,6 +70,7 @@
 # do this after bsd.own.mk.
 .include "kern.opts.mk"
 .include <bsd.compiler.mk>
+.include "config.mk"
 
 .SUFFIXES: .out .o .c .cc .cxx .C .y .l .s .S
 
@@ -163,6 +164,11 @@
 .endfor
 .endif
 
+# Conditionally include SRCS based on kernel config options.
+.for _o in ${KERN_OPTS}
+SRCS+=${SRCS.${_o}}
+.endfor
+
 OBJS+=	${SRCS:N*.h:R:S/$/.o/g}
 
 .if !defined(PROG)
@@ -316,34 +322,6 @@
 	${KMODUNLOAD} -v ${PROG}
 .endif
 
-# Generate options files that otherwise would be built
-# in substantially similar ways through the tree. Move
-# the code here when they all produce identical results
-# (or should)
-.if !defined(KERNBUILDDIR)
-opt_bpf.h:
-	echo "#define DEV_BPF 1" > ${.TARGET}
-.if ${MK_INET_SUPPORT} != "no"
-opt_inet.h:
-	@echo "#define INET 1" > ${.TARGET}
-	@echo "#define TCP_OFFLOAD 1" >> ${.TARGET}
-.endif
-.if ${MK_INET6_SUPPORT} != "no"
-opt_inet6.h:
-	@echo "#define INET6 1" > ${.TARGET}
-.endif
-opt_mrouting.h:
-	echo "#define MROUTING 1" > ${.TARGET}
-opt_natm.h:
-	echo "#define NATM 1" > ${.TARGET}
-opt_scsi.h:
-	echo "#define SCSI_DELAY 15000" > ${.TARGET}
-opt_wlan.h:
-	echo "#define IEEE80211_DEBUG 1" > ${.TARGET}
-	echo "#define IEEE80211_AMPDU_AGE 1" >> ${.TARGET}
-	echo "#define IEEE80211_SUPPORT_MESH 1" >> ${.TARGET}
-.endif
-
 .if defined(KERNBUILDDIR)
 .PATH: ${KERNBUILDDIR}
 CFLAGS+=	-I${KERNBUILDDIR}
Index: head/sys/modules/Makefile
===================================================================
--- head/sys/modules/Makefile
+++ head/sys/modules/Makefile
@@ -751,4 +751,8 @@
 	fi
 .endif
 
+.include "${SYSDIR}/conf/config.mk"
+
+SUBDIR:= ${SUBDIR:u:O}
+
 .include <bsd.subdir.mk>