tools: ynl-gen: print prototypes for recursive stuff

We avoid printing forward declarations and prototypes for most
types by sorting things topologically. But if structs nest we
do need the forward declarations, there's no other way.
Reviewed-by: Donald Hunter <donald.hunter@gmail.com>
Link: https://lore.kernel.org/r/20231213231432.2944749-9-kuba@kernel.orgSigned-off-by: Jakub Kicinski <kuba@kernel.org>

tools/net/ynl/ynl-gen-c.py

@@ -1521,6 +1521,10 @@ def print_dump_prototype(ri):
     print_prototype(ri, "request")
 
 
+def put_typol_fwd(cw, struct):
+    cw.p(f'extern struct ynl_policy_nest {struct.render_name}_nest;')
+
+
 def put_typol(cw, struct):
     type_max = struct.attr_set.max_name
     cw.block_start(line=f'struct ynl_policy_attr {struct.render_name}_policy[{type_max} + 1] =')
@@ -1594,12 +1598,17 @@ def put_enum_to_str(family, cw, enum):
     _put_enum_to_str_helper(cw, enum.render_name, map_name, 'value', enum=enum)
 
 
-def put_req_nested(ri, struct):
+def put_req_nested_prototype(ri, struct, suffix=';'):
     func_args = ['struct nlmsghdr *nlh',
                  'unsigned int attr_type',
                  f'{struct.ptr_name}obj']
 
-    ri.cw.write_func_prot('int', f'{struct.render_name}_put', func_args)
+    ri.cw.write_func_prot('int', f'{struct.render_name}_put', func_args,
+                          suffix=suffix)
+
+
+def put_req_nested(ri, struct):
+    put_req_nested_prototype(ri, struct, suffix='')
     ri.cw.block_start()
     ri.cw.write_func_lvar('struct nlattr *nest;')
 
@@ -1726,18 +1735,23 @@ def _multi_parse(ri, struct, init_lines, local_vars):
     ri.cw.nl()
 
 
-def parse_rsp_nested(ri, struct):
+def parse_rsp_nested_prototype(ri, struct, suffix=';'):
     func_args = ['struct ynl_parse_arg *yarg',
                  'const struct nlattr *nested']
     for arg in struct.inherited:
         func_args.append('__u32 ' + arg)
 
+    ri.cw.write_func_prot('int', f'{struct.render_name}_parse', func_args,
+                          suffix=suffix)
+
+
+def parse_rsp_nested(ri, struct):
+    parse_rsp_nested_prototype(ri, struct, suffix='')
+
     local_vars = ['const struct nlattr *attr;',
                   f'{struct.ptr_name}dst = yarg->data;']
     init_lines = []
 
-    ri.cw.write_func_prot('int', f'{struct.render_name}_parse', func_args)
-
     _multi_parse(ri, struct, init_lines, local_vars)
 
 
@@ -2051,6 +2065,10 @@ def _free_type(ri, direction, struct):
     ri.cw.nl()
 
 
+def free_rsp_nested_prototype(ri):
+        print_free_prototype(ri, "")
+
+
 def free_rsp_nested(ri, struct):
     _free_type(ri, "", struct)
 
@@ -2818,7 +2836,14 @@ def main():
                     put_enum_to_str(parsed, cw, const)
             cw.nl()
 
+            has_recursive_nests = False
             cw.p('/* Policies */')
+            for struct in parsed.pure_nested_structs.values():
+                if struct.recursive:
+                    put_typol_fwd(cw, struct)
+                    has_recursive_nests = True
+            if has_recursive_nests:
+                cw.nl()
             for name in parsed.pure_nested_structs:
                 struct = Struct(parsed, name)
                 put_typol(cw, struct)
@@ -2827,6 +2852,15 @@ def main():
                 put_typol(cw, struct)
 
             cw.p('/* Common nested types */')
+            if has_recursive_nests:
+                for attr_set, struct in parsed.pure_nested_structs.items():
+                    ri = RenderInfo(cw, parsed, args.mode, "", "", attr_set)
+                    free_rsp_nested_prototype(ri)
+                    if struct.request:
+                        put_req_nested_prototype(ri, struct)
+                    if struct.reply:
+                        parse_rsp_nested_prototype(ri, struct)
+                cw.nl()
             for attr_set, struct in parsed.pure_nested_structs.items():
                 ri = RenderInfo(cw, parsed, args.mode, "", "", attr_set)