9p: document missing enum values in kernel-doc comments

Add kernel-doc entries for all undocumented enum values:
- p9_debug_flags: P9_DEBUG_CACHE, P9_DEBUG_MMAP
- p9_msg_t: all 9P2000.L message types (TLOPEN/RLOPEN through
  TUNLINKAT/RUNLINKAT)
- p9_open_mode_t: P9L_MODE_MASK, P9L_DIRECT, P9L_NOWRITECACHE,
  P9L_LOOSE

Assisted-by: Claude:claude-opus-4-6
Signed-off-by: Kit Dallege <xaum.io@gmail.com>
Reviewed-by: Christian Schoenebeck <linux_oss@crudebyte.com>
Message-ID: <20260315190633.73536-1-xaum.io@gmail.com>
Signed-off-by: Dominique Martinet <asmadeus@codewreck.org>

Author: kovan

include/net/9p/9p.h

@@ -24,6 +24,8 @@
  * @P9_DEBUG_PKT: packet marshalling/unmarshalling
  * @P9_DEBUG_FSC: FS-cache tracing
  * @P9_DEBUG_VPKT: Verbose packet debugging (full packet dump)
+ * @P9_DEBUG_CACHE: cache operations tracing
+ * @P9_DEBUG_MMAP: memory-mapped I/O tracing
  *
  * These flags are passed at mount time to turn on various levels of
  * verbosity and tracing which will be output to the system logs.
@@ -68,13 +70,39 @@ void _p9_debug(enum p9_debug_flags level, const char *func,
  * @P9_RSYMLINK: make symlink response
  * @P9_TMKNOD: create a special file object request
  * @P9_RMKNOD: create a special file object response
+ * @P9_TLOPEN: open a file for I/O (9P2000.L)
+ * @P9_RLOPEN: response with qid and iounit (9P2000.L)
  * @P9_TLCREATE: prepare a handle for I/O on an new file for 9P2000.L
  * @P9_RLCREATE: response with file access information for 9P2000.L
  * @P9_TRENAME: rename request
  * @P9_RRENAME: rename response
- * @P9_TMKDIR: create a directory request
- * @P9_RMKDIR: create a directory response
- * @P9_TVERSION: version handshake request
+ * @P9_TREADLINK: read symbolic link target (9P2000.L)
+ * @P9_RREADLINK: response with symbolic link target (9P2000.L)
+ * @P9_TGETATTR: get file attributes request (9P2000.L)
+ * @P9_RGETATTR: get file attributes response (9P2000.L)
+ * @P9_TSETATTR: set file attributes request (9P2000.L)
+ * @P9_RSETATTR: set file attributes response (9P2000.L)
+ * @P9_TXATTRWALK: prepare to read/list extended attributes (9P2000.L)
+ * @P9_RXATTRWALK: response with extended attribute size (9P2000.L)
+ * @P9_TXATTRCREATE: prepare to set extended attribute (9P2000.L)
+ * @P9_RXATTRCREATE: set extended attribute response (9P2000.L)
+ * @P9_TREADDIR: read directory entries request (9P2000.L)
+ * @P9_RREADDIR: read directory entries response (9P2000.L)
+ * @P9_TFSYNC: flush cached file data to storage request (9P2000.L)
+ * @P9_RFSYNC: flush cached file data to storage response (9P2000.L)
+ * @P9_TLOCK: acquire or release a POSIX record lock (9P2000.L)
+ * @P9_RLOCK: POSIX record lock response (9P2000.L)
+ * @P9_TGETLOCK: test for existence of POSIX record lock (9P2000.L)
+ * @P9_RGETLOCK: POSIX record lock test response (9P2000.L)
+ * @P9_TLINK: create a hard link (9P2000.L)
+ * @P9_RLINK: hard link response (9P2000.L)
+ * @P9_TRENAMEAT: safely rename across directories (9P2000.L)
+ * @P9_RRENAMEAT: rename response (9P2000.L)
+ * @P9_TUNLINKAT: unlink a file or directory (9P2000.L)
+ * @P9_RUNLINKAT: unlink response (9P2000.L)
+ * @P9_TMKDIR: create a directory request (9P2000.L)
+ * @P9_RMKDIR: create a directory response (9P2000.L)
+ * @P9_TVERSION: negotiate protocol version and message size
  * @P9_RVERSION: version handshake response
  * @P9_TAUTH: request to establish authentication channel
  * @P9_RAUTH: response with authentication information
@@ -194,6 +222,10 @@ enum p9_msg_t {
  * @P9_ORCLOSE: remove the file when the file is closed
  * @P9_OAPPEND: open the file and seek to the end
  * @P9_OEXCL: only create a file, do not open it
+ * @P9L_MODE_MASK: mask for protocol mode bits (client-side only)
+ * @P9L_DIRECT: disable client-side caching for this file
+ * @P9L_NOWRITECACHE: disable write caching for this file
+ * @P9L_LOOSE: enable loose cache consistency
  *
  * 9P open modes differ slightly from Posix standard modes.
  * In particular, there are extra modes which specify different