kbuild: Add dependency info to modules

During postprocessing, we get the information which modules we depend on 
(i.e. which modules export symbols we need to import) for free, so we
record it in .modinfo. This may allow us to remove the "depmod" program
at a later time, though for now it remains working as usual.

scripts/modpost.c

@@ -75,6 +75,7 @@ struct module {
 	struct module *next;
 	const char *name;
 	struct symbol *unres;
+	int seen;
 };
 
 static struct module *modules;
@@ -317,6 +318,39 @@ add_versions(struct buffer *b, struct module *mod)
 	buf_printf(b, "};\n");
 }
 
+void
+add_depends(struct buffer *b, struct module *mod, struct module *modules)
+{
+	struct symbol *s;
+	struct module *m;
+	int first = 1;
+
+	for (m = modules; m; m = m->next) {
+		if (strcmp(m->name, "vmlinux") == 0)
+			m->seen = 1;
+		else 
+			m->seen = 0;
+	}
+
+	buf_printf(b, "\n");
+	buf_printf(b, "static const char __module_depends[]\n");
+	buf_printf(b, "__attribute__((section(\".modinfo\"))) =\n");
+	buf_printf(b, "\"depends=");
+	for (s = mod->unres; s; s = s->next) {
+		if (!s->module)
+			continue;
+
+		if (s->module->seen)
+			continue;
+
+		s->module->seen = 1;
+		buf_printf(b, "%s%s", first ? "" : ",",
+			   strrchr(s->module->name, '/') + 1);
+		first = 0;
+	}
+	buf_printf(b, "\";\n");
+}
+
 void
 write_if_changed(struct buffer *b, const char *fname)
 {
@@ -387,6 +421,7 @@ main(int argc, char **argv)
 
 		add_header(&buf);
 		add_versions(&buf, mod);
+		add_depends(&buf, mod, modules);
 
 		sprintf(fname, "%s.ver.c", mod->name);
 		write_if_changed(&buf, fname);