v9fs:add Documentation

Signed-off-by: chenrun1 <chenrun1@xiaomi.com>

Documentation/components/filesystem/index.rst

@@ -557,6 +557,7 @@ NuttX provides support for a variety of file systems out of the box.
   nxflat.rst
   pseudofs.rst
   special_files_dev_num.rst
+  v9fs.rst
 
 FS Categories
 -------------

Documentation/components/filesystem/v9fs.rst

@@ -0,0 +1,94 @@
+V9FS
+====
+
+V9FS is a remote file system based on the 9P2000.L protocol.
+
+Adding V9FS to the NuttX Configuration
+======================================
+
+The V9FS client is easy to add to your configuration. Just add
+``CONFIG_FS_V9FS`` to ``nuttx/.config``.
+
+In order to fully run V9FS, you also need to select a transport layer
+driver. The two currently available are:
+
+  - **VIRTIO** -> ``CONFIG_V9FS_VIRTIO_9P=y``
+  - **SOCKET** -> ``CONFIG_V9FS_SOCKET_9P=y``
+
+NFS Mount Command
+=================
+
+In V9FS, we have some special parameters
+
+  - ``uname``. Used to indicate the user identity of the client
+  - ``aname``. Optional, it specifies the file tree that the client requests to access
+  - ``trans``. Selects the transport layer (virtio/socket)
+  - ``msize``. The maximum size of the message
+  - ``tag``. The tag of the mount point
+
+Different transport layers have different requirements for parameter
+passing. Here are some examples:
+
+Qemu + VIRTIO
+--------------
+
+.. code-block:: console
+
+  mount -t v9fs -o trans=virtio,tag=<mount_tag> /dir
+
+Similarly, we need to bring the corresponding parameters in qemu
+
+.. code-block:: console
+
+  -fsdev local,security_model=none,id=fsdev1,path=<share-path> \
+  -device virtio-9p-device,id=fs1,fsdev=fsdev1,mount_tag=<mount_tag>
+
+For how to start virtio-9p in QEMU, please refer to the document:
+
+  - https://wiki.qemu.org/Documentation/9psetup
+
+
+
+Socket
+-------
+
+.. code-block:: console
+
+  mount -t v9fs -o trans=socket,tag=<IP Address>:[Port Default 563],aname=[path] /dir
+
+There are many types of 9P socket servers. Here we use R9-fileserver
+(a cross-platform 9p server based on Rust
+https://github.com/crafcat7/R9-fileserver)
+
+.. code-block:: console
+
+  sudo ./ya-vm-file-server --network-address <IP Address>:<Server Port> --mount-point <share-path>
+
+
+Result
+------
+
+.. code-block:: fish
+
+  NuttShell (NSH)
+  nsh> mkdir mnt
+  nsh> 
+  nsh> ls mnt
+  /mnt:
+  nsh> mount -t v9fs -o trans=virtio,tag=hostshare /mnt/v9fs
+  nsh> 
+  nsh> ls /mnt/v9fs
+  /mnt/v9fs:
+  sdcard/
+  mnt/
+  nsh> 
+  nsh> echo "This is a test" >/mnt/v9fs/testfile.txt
+  nsh> ls -l /mnt/v9fs
+  /mnt/v9fs:
+  drwxrwxrwx    1000    1000        4096 sdcard/
+  -rw-rw-rw-    1000    1000          15 testfile.txt
+  drwxrwxrwx    1000    1000        4096 mnt/
+  nsh> 
+  nsh> cat /mnt/v9fs/testfile.txt
+  This is a test
+  nsh>