9p: Documentation updates

The kernel-doc comments of much of the 9p system have been in disarray since
reorganization.  This patch fixes those problems, adds additional documentation
and a template book which collects the 9p information.

Signed-off-by: Eric Van Hensbergen <ericvh@gmail.com>

3 files changed, 287 insertions, 30 deletions

diff --git a/include/net/9p/9p.h b/include/net/9p/9p.h
index 585eb4496990..7bfb2f2e423c 100644
--- a/include/net/9p/9p.h
+++ b/include/net/9p/9p.h
@@ -29,14 +29,31 @@
 
 #ifdef CONFIG_NET_9P_DEBUG
 
-#define P9_DEBUG_ERROR          (1<<0)
-#define P9_DEBUG_9P             (1<<2)
-#define P9_DEBUG_VFS            (1<<3)
-#define P9_DEBUG_CONV           (1<<4)
-#define P9_DEBUG_MUX            (1<<5)
-#define P9_DEBUG_TRANS          (1<<6)
-#define P9_DEBUG_SLABS          (1<<7)
-#define P9_DEBUG_FCALL          (1<<8)
+/**
+ * enum p9_debug_flags - bits for mount time debug parameter
+ * @P9_DEBUG_ERROR: more verbose error messages including original error string
+ * @P9_DEBUG_9P: 9P protocol tracing
+ * @P9_DEBUG_VFS: VFS API tracing
+ * @P9_DEBUG_CONV: protocol conversion tracing
+ * @P9_DEBUG_MUX: trace management of concurrent transactions
+ * @P9_DEBUG_TRANS: transport tracing
+ * @P9_DEBUG_SLABS: memory management tracing
+ * @P9_DEBUG_FCALL: verbose dump of protocol messages
+ *
+ * These flags are passed at mount time to turn on various levels of
+ * verbosity and tracing which will be output to the system logs.
+ */
+
+enum p9_debug_flags {
+        P9_DEBUG_ERROR =        (1<<0),
+        P9_DEBUG_9P =           (1<<2),
+        P9_DEBUG_VFS =          (1<<3),
+        P9_DEBUG_CONV =         (1<<4),
+        P9_DEBUG_MUX =          (1<<5),
+        P9_DEBUG_TRANS =        (1<<6),
+        P9_DEBUG_SLABS =        (1<<7),
+        P9_DEBUG_FCALL =        (1<<8),
+};
 
 extern unsigned int p9_debug_level;
 
@@ -62,9 +79,47 @@ do { \
                 format , __FUNCTION__, task_pid_nr(current), ## arg); \
 } while (0)
 
+/**
+ * enum p9_msg_t - 9P message types
+ * @P9_TVERSION: version handshake request
+ * @P9_RVERSION: version handshake response
+ * @P9_TAUTH: request to establish authentication channel
+ * @P9_RAUTH: response with authentication information
+ * @P9_TATTACH: establish user access to file service
+ * @P9_RATTACH: response with top level handle to file hierarchy
+ * @P9_TERROR: not used
+ * @P9_RERROR: response for any failed request
+ * @P9_TFLUSH: request to abort a previous request
+ * @P9_RFLUSH: response when previous request has been cancelled
+ * @P9_TWALK: descend a directory hierarchy
+ * @P9_RWALK: response with new handle for position within hierarchy
+ * @P9_TOPEN: prepare a handle for I/O on an existing file
+ * @P9_ROPEN: response with file access information
+ * @P9_TCREATE: prepare a handle for I/O on a new file
+ * @P9_RCREATE: response with file access information
+ * @P9_TREAD: request to transfer data from a file or directory
+ * @P9_RREAD: response with data requested
+ * @P9_TWRITE: reuqest to transfer data to a file
+ * @P9_RWRITE: response with out much data was transfered to file
+ * @P9_TCLUNK: forget about a handle to an entity within the file system
+ * @P9_RCLUNK: response when server has forgotten about the handle
+ * @P9_TREMOVE: request to remove an entity from the hierarchy
+ * @P9_RREMOVE: response when server has removed the entity
+ * @P9_TSTAT: request file entity attributes
+ * @P9_RSTAT: response with file entity attributes
+ * @P9_TWSTAT: request to update file entity attributes
+ * @P9_RWSTAT: response when file entity attributes are updated
+ *
+ * There are 14 basic operations in 9P2000, paired as
+ * requests and responses.  The one special case is ERROR
+ * as there is no @P9_TERROR request for clients to transmit to
+ * the server, but the server may respond to any other request
+ * with an @P9_RERROR.
+ *
+ * See Also: http://plan9.bell-labs.com/sys/man/5/INDEX.html
+ */
 
-/* Message Types */
-enum {
+enum p9_msg_t {
         P9_TVERSION = 100,
         P9_RVERSION,
         P9_TAUTH = 102,
@@ -95,30 +150,71 @@ enum {
         P9_RWSTAT,
 };
 
-/* open modes */
-enum {
+/**
+ * enum p9_open_mode_t - 9P open modes
+ * @P9_OREAD: open file for reading only
+ * @P9_OWRITE: open file for writing only
+ * @P9_ORDWR: open file for reading or writing
+ * @P9_OEXEC: open file for execution
+ * @P9_OTRUNC: truncate file to zero-length before opening it
+ * @P9_OREXEC: close the file when an exec(2) system call is made
+ * @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
+ *
+ * 9P open modes differ slightly from Posix standard modes.
+ * In particular, there are extra modes which specify different
+ * semantic behaviors than may be available on standard Posix
+ * systems.  For example, @P9_OREXEC and @P9_ORCLOSE are modes that
+ * most likely will not be issued from the Linux VFS client, but may
+ * be supported by servers.
+ *
+ * See Also: http://plan9.bell-labs.com/magic/man2html/2/open
+ */
+
+enum p9_open_mode_t {
         P9_OREAD = 0x00,
         P9_OWRITE = 0x01,
         P9_ORDWR = 0x02,
         P9_OEXEC = 0x03,
-        P9_OEXCL = 0x04,
         P9_OTRUNC = 0x10,
         P9_OREXEC = 0x20,
         P9_ORCLOSE = 0x40,
         P9_OAPPEND = 0x80,
-};
-
-/* permissions */
-enum {
+        P9_OEXCL = 0x1000,
+};
+
+/**
+ * enum p9_perm_t - 9P permissions
+ * @P9_DMDIR: mode bite for directories
+ * @P9_DMAPPEND: mode bit for is append-only
+ * @P9_DMEXCL: mode bit for excluse use (only one open handle allowed)
+ * @P9_DMMOUNT: mode bite for mount points
+ * @P9_DMAUTH: mode bit for authentication file
+ * @P9_DMTMP: mode bit for non-backed-up files
+ * @P9_DMSYMLINK: mode bit for symbolic links (9P2000.u)
+ * @P9_DMLINK: mode bit for hard-link (9P2000.u)
+ * @P9_DMDEVICE: mode bit for device files (9P2000.u)
+ * @P9_DMNAMEDPIPE: mode bit for named pipe (9P2000.u)
+ * @P9_DMSOCKET: mode bit for socket (9P2000.u)
+ * @P9_DMSETUID: mode bit for setuid (9P2000.u)
+ * @P9_DMSETGID: mode bit for setgid (9P2000.u)
+ * @P9_DMSETVTX: mode bit for sticky bit (9P2000.u)
+ *
+ * 9P permissions differ slightly from Posix standard modes.
+ *
+ * See Also: http://plan9.bell-labs.com/magic/man2html/2/stat
+ */
+enum p9_perm_t {
         P9_DMDIR = 0x80000000,
         P9_DMAPPEND = 0x40000000,
         P9_DMEXCL = 0x20000000,
         P9_DMMOUNT = 0x10000000,
         P9_DMAUTH = 0x08000000,
         P9_DMTMP = 0x04000000,
+/* 9P2000.u extensions */
         P9_DMSYMLINK = 0x02000000,
         P9_DMLINK = 0x01000000,
-        /* 9P2000.u extensions */
         P9_DMDEVICE = 0x00800000,
         P9_DMNAMEDPIPE = 0x00200000,
         P9_DMSOCKET = 0x00100000,
@@ -127,8 +223,26 @@ enum {
         P9_DMSETVTX = 0x00010000,
 };
 
-/* qid.types */
-enum {
+/**
+ * enum p9_qid_t - QID types
+ * @P9_QTDIR: directory
+ * @P9_QTAPPEND: append-only
+ * @P9_QTEXCL: excluse use (only one open handle allowed)
+ * @P9_QTMOUNT: mount points
+ * @P9_QTAUTH: authentication file
+ * @P9_QTTMP: non-backed-up files
+ * @P9_QTSYMLINK: symbolic links (9P2000.u)
+ * @P9_QTLINK: hard-link (9P2000.u)
+ * @P9_QTFILE: normal files
+ *
+ * QID types are a subset of permissions - they are primarily
+ * used to differentiate semantics for a file system entity via
+ * a jump-table.  Their value is also the most signifigant 16 bits
+ * of the permission_t
+ *
+ * See Also: http://plan9.bell-labs.com/magic/man2html/2/stat
+ */
+enum p9_qid_t {
         P9_QTDIR = 0x80,
         P9_QTAPPEND = 0x40,
         P9_QTEXCL = 0x20,
@@ -140,6 +254,7 @@ enum {
         P9_QTFILE = 0x00,
 };
 
+/* 9P Magic Numbers */
 #define P9_NOTAG        (u16)(~0)
 #define P9_NOFID        (u32)(~0)
 #define P9_MAXWELEM     16
@@ -147,19 +262,69 @@ enum {
 /* ample room for Twrite/Rread header */
 #define P9_IOHDRSZ      24
 
+/**
+ * struct p9_str - length prefixed string type
+ * @len: length of the string
+ * @str: the string
+ *
+ * The protocol uses length prefixed strings for all
+ * string data, so we replicate that for our internal
+ * string members.
+ */
+
 struct p9_str {
         u16 len;
         char *str;
 };
 
-/* qids are the unique ID for a file (like an inode */
+/**
+ * struct p9_qid - file system entity information
+ * @type: 8-bit type &p9_qid_t
+ * @version: 16-bit monotonically incrementing version number
+ * @path: 64-bit per-server-unique ID for a file system element
+ *
+ * qids are identifiers used by 9P servers to track file system
+ * entities.  The type is used to differentiate semantics for operations
+ * on the entity (ie. read means something different on a directory than
+ * on a file).  The path provides a server unique index for an entity
+ * (roughly analogous to an inode number), while the version is updated
+ * every time a file is modified and can be used to maintain cache
+ * coherency between clients and serves.
+ * Servers will often differentiate purely synthetic entities by setting
+ * their version to 0, signaling that they should never be cached and
+ * should be accessed synchronously.
+ *
+ * See Also://plan9.bell-labs.com/magic/man2html/2/stat
+ */
+
 struct p9_qid {
         u8 type;
         u32 version;
         u64 path;
 };
 
-/* Plan 9 file metadata (stat) structure */
+/**
+ * struct p9_stat - file system metadata information
+ * @size: length prefix for this stat structure instance
+ * @type: the type of the server (equivilent to a major number)
+ * @dev: the sub-type of the server (equivilent to a minor number)
+ * @qid: unique id from the server of type &p9_qid
+ * @mode: Plan 9 format permissions of type &p9_perm_t
+ * @atime: Last access/read time
+ * @mtime: Last modify/write time
+ * @length: file length
+ * @name: last element of path (aka filename) in type &p9_str
+ * @uid: owner name in type &p9_str
+ * @gid: group owner in type &p9_str
+ * @muid: last modifier in type &p9_str
+ * @extension: area used to encode extended UNIX support in type &p9_str
+ * @n_uid: numeric user id of owner (part of 9p2000.u extension)
+ * @n_gid: numeric group id (part of 9p2000.u extension)
+ * @n_muid: numeric user id of laster modifier (part of 9p2000.u extension)
+ *
+ * See Also: http://plan9.bell-labs.com/magic/man2html/2/stat
+ */
+
 struct p9_stat {
         u16 size;
         u16 type;
@@ -179,10 +344,14 @@ struct p9_stat {
         u32 n_muid;                     /* 9p2000.u extensions */
 };
 
-/* file metadata (stat) structure used to create Twstat message
-   The is similar to p9_stat, but the strings don't point to
-   the same memory block and should be freed separately
-*/
+/*
+ * file metadata (stat) structure used to create Twstat message
+ * The is identical to &p9_stat, but the strings don't point to
+ * the same memory block and should be freed separately
+ *
+ * See Also: http://plan9.bell-labs.com/magic/man2html/2/stat
+ */
+
 struct p9_wstat {
         u16 size;
         u16 type;
@@ -335,10 +504,20 @@ struct p9_twstat {
 struct p9_rwstat {
 };
 
-/*
-  * fcall is the primary packet structure
-  *
-  */
+/**
+ * struct p9_fcall - primary packet structure
+ * @size: prefixed length of the structure
+ * @id: protocol operating identifier of type &p9_msg_t
+ * @tag: transaction id of the request
+ * @sdata: payload
+ * @params: per-operation parameters
+ *
+ * &p9_fcall represents the structure for all 9P RPC
+ * transactions.  Requests are packaged into fcalls, and reponses
+ * must be extracted from them.
+ *
+ * See Also: http://plan9.bell-labs.com/magic/man2html/2/fcall
+ */
 
 struct p9_fcall {
         u32 size;
diff --git a/include/net/9p/client.h b/include/net/9p/client.h
index e52f93d9ac5f..c936dd14de41 100644
--- a/include/net/9p/client.h
+++ b/include/net/9p/client.h
@@ -26,6 +26,23 @@
 #ifndef NET_9P_CLIENT_H
 #define NET_9P_CLIENT_H
 
+/**
+ * struct p9_client - per client instance state
+ * @lock: protect @fidlist
+ * @msize: maximum data size negotiated by protocol
+ * @dotu: extension flags negotiated by protocol
+ * @trans_mod: module API instantiated with this client
+ * @trans: tranport instance state and API
+ * @conn: connection state information used by trans_fd
+ * @fidpool: fid handle accounting for session
+ * @fidlist: List of active fid handles
+ *
+ * The client structure is used to keep track of various per-client
+ * state that has been instantiated.
+ *
+ * Bugs: duplicated data and potentially unnecessary elements.
+ */
+
 struct p9_client {
         spinlock_t lock; /* protect client structure */
         int msize;
@@ -38,6 +55,24 @@ struct p9_client {
         struct list_head fidlist;
 };
 
+/**
+ * struct p9_fid - file system entity handle
+ * @clnt: back pointer to instantiating &p9_client
+ * @fid: numeric identifier for this handle
+ * @mode: current mode of this fid (enum?)
+ * @qid: the &p9_qid server identifier this handle points to
+ * @iounit: the server reported maximum transaction size for this file
+ * @uid: the numeric uid of the local user who owns this handle
+ * @aux: transport specific information (unused?)
+ * @rdir_fpos: tracks offset of file position when reading directory contents
+ * @rdir_pos: (unused?)
+ * @rdir_fcall: holds response of last directory read request
+ * @flist: per-client-instance fid tracking
+ * @dlist: per-dentry fid tracking
+ *
+ * TODO: This needs lots of explanation.
+ */
+
 struct p9_fid {
         struct p9_client *clnt;
         u32 fid;
diff --git a/include/net/9p/transport.h b/include/net/9p/transport.h
index d2209ae9d18b..240e0de888c6 100644
--- a/include/net/9p/transport.h
+++ b/include/net/9p/transport.h
@@ -26,12 +26,40 @@
 #ifndef NET_9P_TRANSPORT_H
 #define NET_9P_TRANSPORT_H
 
+/**
+ * enum p9_trans_status - different states of underlying transports
+ * @Connected: transport is connected and healthy
+ * @Disconnected: transport has been disconnected
+ * @Hung: transport is connected by wedged
+ *
+ * This enumeration details the various states a transport
+ * instatiation can be in.
+ */
+
 enum p9_trans_status {
         Connected,
         Disconnected,
         Hung,
 };
 
+/**
+ * struct p9_trans - per-transport state and API
+ * @status: transport &p9_trans_status
+ * @msize: negotiated maximum packet size (duplicate from client)
+ * @extended: negotiated protocol extensions (duplicate from client)
+ * @priv: transport private data
+ * @close: member function to disconnect and close the transport
+ * @rpc: member function to issue a request to the transport
+ *
+ * This is the basic API for a transport instance.  It is used as
+ * a handle by the client to issue requests.  This interface is currently
+ * in flux during reorganization.
+ *
+ * Bugs: there is lots of duplicated data here and its not clear that
+ * the member functions need to be per-instance versus per transport
+ * module.
+ */
+
 struct p9_trans {
         enum p9_trans_status status;
         int msize;
@@ -42,6 +70,21 @@ struct p9_trans {
                                                         struct p9_fcall **rc);
 };
 
+/**
+ * struct p9_trans_module - transport module interface
+ * @list: used to maintain a list of currently available transports
+ * @name: the human-readable name of the transport
+ * @maxsize: transport provided maximum packet size
+ * @def: set if this transport should be considered the default
+ * @create: member function to create a new connection on this transport
+ *
+ * This is the basic API for a transport module which is registered by the
+ * transport module with the 9P core network module and used by the client
+ * to instantiate a new connection on a transport.
+ *
+ * Bugs: the transport module list isn't protected.
+ */
+
 struct p9_trans_module {
         struct list_head list;
         char *name;             /* name of transport */