tools: ynl-gen: support empty attribute lists

Differentiate between empty list and None for member lists.
New families may want to create request responses with no attribute.
If we treat those the same as None we end up rendering
a full parsing policy in user space, instead of an empty one.

Reviewed-by: Donald Hunter <donald.hunter@gmail.com>
Link: https://lore.kernel.org/r/20230824003056.1436637-5-kuba@kernel.org
Signed-off-by: Jakub Kicinski <kuba@kernel.org>

diff --git a/tools/net/ynl/ynl-gen-c.py b/tools/net/ynl/ynl-gen-c.py
index 13d06931c045ea6477edb3c4c13c4eb339461286..9209bdcca9c61bd88b845178a35c68990e2521f5 100755 (executable)
--- a/tools/net/ynl/ynl-gen-c.py
+++ b/tools/net/ynl/ynl-gen-c.py
@@ -615,7 +615,7 @@ class Struct:
 
         self.attr_list = []
         self.attrs = dict()
-        if type_list:
+        if type_list is not None:
             for t in type_list:
                 self.attr_list.append((t, self.attr_set[t]),)
         else:
@@ -1543,7 +1543,14 @@ def parse_rsp_msg(ri, deref=False):
 
     ri.cw.write_func_prot('int', f'{op_prefix(ri, "reply", deref=deref)}_parse', func_args)
 
-    _multi_parse(ri, ri.struct["reply"], init_lines, local_vars)
+    if ri.struct["reply"].member_list():
+        _multi_parse(ri, ri.struct["reply"], init_lines, local_vars)
+    else:
+        # Empty reply
+        ri.cw.block_start()
+        ri.cw.p('return MNL_CB_OK;')
+        ri.cw.block_end()
+        ri.cw.nl()
 
 
 def print_req(ri):