[RFC PATCH 1/2] docs: automarkup.py: Add literal markup of known constants

[Nícolas F. R. A. Prado <n@xxxxxxxxxxxxx>]

There are some known constants that are used throughout the
documentation, like NULL and error codes, and which are better formatted
as literals by Sphinx. Make these words automatically literals.

Suggested-by: Matthew Wilcox <willy@xxxxxxxxxxxxx>
Signed-off-by: Nícolas F. R. A. Prado <n@xxxxxxxxxxxxx>
---
 Documentation/sphinx/automarkup.py | 45 ++++++++++++++++++++++++++++--
 1 file changed, 43 insertions(+), 2 deletions(-)

diff --git a/Documentation/sphinx/automarkup.py b/Documentation/sphinx/automarkup.py
index acf5473002f3..eb219783d9e3 100644
--- a/Documentation/sphinx/automarkup.py
+++ b/Documentation/sphinx/automarkup.py
@@ -72,6 +72,40 @@ Skipfuncs = [ 'open', 'close', 'read', 'write', 'fcntl', 'mmap',
               'select', 'poll', 'fork', 'execve', 'clone', 'ioctl',
               'socket' ]
 
+#
+# Words that are automatically converted to literals
+#
+Literals = [ 'NULL', 'ULONG_MAX', 'LONG_MAX', 'EPERM', 'ENOENT', 'ESRCH',
+            'EINTR', 'EIO', 'ENXIO', 'E2BIG', 'ENOEXEC', 'EBADF', 'ECHILD',
+            'EAGAIN', 'ENOMEM', 'EACCES', 'EFAULT', 'ENOTBLK', 'EBUSY',
+            'EEXIST', 'EXDEV', 'ENODEV', 'ENOTDIR', 'EISDIR', 'EINVAL',
+            'ENFILE', 'EMFILE', 'ENOTTY', 'ETXTBSY', 'EFBIG', 'ENOSPC',
+            'ESPIPE', 'EROFS', 'EMLINK', 'EPIPE', 'EDOM', 'ERANGE', 'EDEADLK',
+            'ENAMETOOLONG', 'ENOLCK', 'ENOSYS', 'ENOTEMPTY', 'ELOOP',
+            'EWOULDBLOCK', 'ENOMSG', 'EIDRM', 'ECHRNG', 'EL2NSYNC', 'EL3HLT',
+            'EL3RST', 'ELNRNG', 'EUNATCH', 'ENOCSI', 'EL2HLT', 'EBADE', 'EBADR',
+            'EXFULL', 'ENOANO', 'EBADRQC', 'EBADSLT', 'EDEADLOCK', 'EBFONT',
+            'ENOSTR', 'ENODATA', 'ETIME', 'ENOSR', 'ENONET', 'ENOPKG',
+            'EREMOTE', 'ENOLINK', 'EADV', 'ESRMNT', 'ECOMM', 'EPROTO',
+            'EMULTIHOP', 'EDOTDOT', 'EBADMSG', 'EOVERFLOW', 'ENOTUNIQ',
+            'EBADFD', 'EREMCHG', 'ELIBACC', 'ELIBBAD', 'ELIBSCN', 'ELIBMAX',
+            'ELIBEXEC', 'EILSEQ', 'ERESTART', 'ESTRPIPE', 'EUSERS', 'ENOTSOCK',
+            'EDESTADDRREQ', 'EMSGSIZE', 'EPROTOTYPE', 'ENOPROTOOPT',
+            'EPROTONOSUPPORT', 'ESOCKTNOSUPPORT', 'EOPNOTSUPP', 'EPFNOSUPPORT',
+            'EAFNOSUPPORT', 'EADDRINUSE', 'EADDRNOTAVAIL', 'ENETDOWN',
+            'ENETUNREACH', 'ENETRESET', 'ECONNABORTED', 'ECONNRESET', 'ENOBUFS',
+            'EISCONN', 'ENOTCONN', 'ESHUTDOWN', 'ETOOMANYREFS', 'ETIMEDOUT',
+            'ECONNREFUSED', 'EHOSTDOWN', 'EHOSTUNREACH', 'EALREADY',
+            'EINPROGRESS', 'ESTALE', 'EUCLEAN', 'ENOTNAM', 'ENAVAIL', 'EISNAM',
+            'EREMOTEIO', 'EDQUOT', 'ENOMEDIUM', 'EMEDIUMTYPE', 'ECANCELED',
+            'ENOKEY', 'EKEYEXPIRED', 'EKEYREVOKED', 'EKEYREJECTED',
+            'EOWNERDEAD', 'ENOTRECOVERABLE', 'ERFKILL', 'EHWPOISON' ]
+
+#
+# Any of the words in Literals, optionally prefixed with a '-'
+#
+RE_literal = re.compile(r'-?\b(' + str(r'|'.join(Literals)) + r')\b')
+
 c_namespace = ''
 
 def markup_refs(docname, app, node):
@@ -83,14 +117,18 @@ def markup_refs(docname, app, node):
     #
     markup_func_sphinx2 = {RE_doc: markup_doc_ref,
                            RE_function: markup_c_ref,
-                           RE_generic_type: markup_c_ref}
+                           RE_generic_type: markup_c_ref,
+                           RE_literal: markup_literal,
+                           }
 
     markup_func_sphinx3 = {RE_doc: markup_doc_ref,
                            RE_function: markup_func_ref_sphinx3,
                            RE_struct: markup_c_ref,
                            RE_union: markup_c_ref,
                            RE_enum: markup_c_ref,
-                           RE_typedef: markup_c_ref}
+                           RE_typedef: markup_c_ref,
+                           RE_literal: markup_literal,
+                           }
 
     if sphinx.version_info[0] >= 3:
         markup_func = markup_func_sphinx3
@@ -225,6 +263,9 @@ def markup_c_ref(docname, app, match):
 
     return target_text
 
+def markup_literal(docname, app, match):
+    return nodes.literal('', match.group(0))
+
 #
 # Try to replace a documentation reference of the form Documentation/... with a
 # cross reference to that page
-- 
2.32.0