Give zlib the ability to be a module that can be depended on,

in the MODULE_DEPEND() sense.

sys/modules/zlib/Makefile

@@ -0,0 +1,8 @@
+# $FreeBSD$
+
+.PATH: ${.CURDIR}/../../net
+
+KMOD=	zlib
+SRCS=	zlib.c
+
+.include <bsd.kmod.mk>

sys/net/zlib.c

@@ -57,6 +57,8 @@
 #include <sys/time.h>
 #include <sys/systm.h>
 #include <sys/param.h>
+#include <sys/kernel.h>
+#include <sys/module.h>
 #  define HAVE_MEMCPY
 
 #else
@@ -5380,3 +5382,25 @@ uLong adler32(adler, buf, len)
     return (s2 << 16) | s1;
 }
 /* --- adler32.c */
+
+#ifdef _KERNEL
+static int
+zlib_modevent(module_t mod, int type, void *unused)
+{
+	switch (type) {
+	case MOD_LOAD:
+		return 0;
+	case MOD_UNLOAD:
+		return 0;
+	}
+	return EINVAL;
+}
+
+static moduledata_t zlib_mod = {
+	"zlib",
+	zlib_modevent,
+	0
+};
+DECLARE_MODULE(zlib, zlib_mod, SI_SUB_DRIVERS, SI_ORDER_FIRST);
+MODULE_VERSION(zlib, 1);
+#endif /* _KERNEL */