[PATCH net-next 4/4] tools: ynl: fix uapi generation for anonymous enums with documented entries

In pyynl's current render_uapi() implementation there exists a check
that is intended to ensure that definitions of type "enum" or "flags"
have a doc entry before calling write_doc_line().

However, this check still passes for anonymous enums since
enum.has_doc() still evaluates as true, so they still take the kdoc
code path.

As a result, this path attempts to hang the entry docs off of
enum.enum_name (which is of type None), raising a TypeError.
Both the ovs_datapath.yaml and ovs_flow.yaml specs will fail to
generate uapi headers in today's tree:

  $ ynl_gen_c.py --spec Documentation/netlink/specs/ovs_datapath.yaml \
    --mode uapi --header

  Traceback (most recent call last):
    File "tools/net/ynl/pyynl/ynl_gen_c.py", line 3780, in <module>
      main()
      ~~~~^^
    File "tools/net/ynl/pyynl/ynl_gen_c.py", line 3511, in main
      render_uapi(parsed, cw)
      ~~~~~~~~~~~^^^^^^^^^^^^
    File "tools/net/ynl/pyynl/ynl_gen_c.py", line 3255, in render_uapi
      cw.write_doc_line(enum.enum_name + doc)
                        ~~~~~~~~~~~~~~~^~~~~
  TypeError: unsupported operand type(s) for +: 'NoneType' and 'str'

The fix implemented by this patch instead generates a plain comment
in this scenario as there is no kdoc identifier to hang the
documentation off of.

Fixes: 690e50dd69ee ("tools: ynl-gen: de-kdocify enums with no doc for entries")
Signed-off-by: Taylor Bates <redacted>
---
 tools/net/ynl/pyynl/ynl_gen_c.py | 6 ++++--
 1 file changed, 4 insertions(+), 2 deletions(-)

diff --git a/tools/net/ynl/pyynl/ynl_gen_c.py b/tools/net/ynl/pyynl/ynl_gen_c.py
index 1c422141d2d7..66a6dbe07125 100755
--- a/tools/net/ynl/pyynl/ynl_gen_c.py
+++ b/tools/net/ynl/pyynl/ynl_gen_c.py

@@ -3247,15 +3247,17 @@ def render_uapi(family, cw):
                 continue
 
             if enum.has_doc():
-                if enum.has_entry_doc():
+                if enum.has_entry_doc() and enum.enum_name:
                     cw.p('/**')
                     doc = ''
                     if 'doc' in enum:
                         doc = ' - ' + enum['doc']
                     cw.write_doc_line(enum.enum_name + doc)
                 else:
+                    # Render a plain comment, no kdoc identifier available
                     cw.p('/*')
-                    cw.write_doc_line(enum['doc'], indent=False)
+                    if 'doc' in enum:
+                        cw.write_doc_line(enum['doc'], indent=False)
                 for entry in enum.entries.values():
                     if entry.has_doc():
                         doc = '@' + entry.c_name + ': ' + entry['doc']

-- 
2.55.0