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Diffstat (limited to 'Documentation/filesystems/9p.rst')
| -rw-r--r-- | Documentation/filesystems/9p.rst | 60 |
1 files changed, 58 insertions, 2 deletions
diff --git a/Documentation/filesystems/9p.rst b/Documentation/filesystems/9p.rst index 1e0e0bb6fdf9..2bbf68b56b0d 100644 --- a/Documentation/filesystems/9p.rst +++ b/Documentation/filesystems/9p.rst @@ -31,7 +31,7 @@ Other applications are described in the following papers: * PROSE I/O: Using 9p to enable Application Partitions http://plan9.escet.urjc.es/iwp9/cready/PROSE_iwp9_2006.pdf * VirtFS: A Virtualization Aware File System pass-through - http://goo.gl/3WPDg + https://kernel.org/doc/ols/2010/ols2010-pages-109-120.pdf Usage ===== @@ -48,11 +48,66 @@ For server running on QEMU host with virtio transport:: mount -t 9p -o trans=virtio <mount_tag> /mnt/9 -where mount_tag is the tag associated by the server to each of the exported +where mount_tag is the tag generated by the server to each of the exported mount points. Each 9P export is seen by the client as a virtio device with an associated "mount_tag" property. Available mount tags can be seen by reading /sys/bus/virtio/drivers/9pnet_virtio/virtio<n>/mount_tag files. +USBG Usage +========== + +To mount a 9p FS on a USB Host accessible via the gadget at runtime:: + + mount -t 9p -o trans=usbg,aname=/path/to/fs <device> /mnt/9 + +To mount a 9p FS on a USB Host accessible via the gadget as root filesystem:: + + root=<device> rootfstype=9p rootflags=trans=usbg,cache=loose,uname=root,access=0,dfltuid=0,dfltgid=0,aname=/path/to/rootfs + +where <device> is the tag associated by the usb gadget transport. +It is defined by the configfs instance name. + +USBG Example +============ + +The USB host exports a filesystem, while the gadget on the USB device +side makes it mountable. + +Diod (9pfs server) and the forwarder are on the development host, where +the root filesystem is actually stored. The gadget is initialized during +boot (or later) on the embedded board. Then the forwarder will find it +on the USB bus and start forwarding requests. + +In this case the 9p requests come from the device and are handled by the +host. The reason is that USB device ports are normally not available on +PCs, so a connection in the other direction would not work. + +When using the usbg transport, for now there is no native usb host +service capable to handle the requests from the gadget driver. For +this we have to use the extra python tool p9_fwd.py from tools/usb. + +Just start the 9pfs capable network server like diod/nfs-ganesha e.g.:: + + $ diod -f -n -d 0 -S -l 0.0.0.0:9999 -e $PWD + +Optionaly scan your bus if there are more then one usbg gadgets to find their path:: + + $ python $kernel_dir/tools/usb/p9_fwd.py list + + Bus | Addr | Manufacturer | Product | ID | Path + --- | ---- | ---------------- | ---------------- | --------- | ---- + 2 | 67 | unknown | unknown | 1d6b:0109 | 2-1.1.2 + 2 | 68 | unknown | unknown | 1d6b:0109 | 2-1.1.3 + +Then start the python transport:: + + $ python $kernel_dir/tools/usb/p9_fwd.py --path 2-1.1.2 connect -p 9999 + +After that the gadget driver can be used as described above. + +One use-case is to use it as an alternative to NFS root booting during +the development of embedded Linux devices. + Options ======= @@ -68,6 +123,7 @@ Options virtio connect to the next virtio channel available (from QEMU with trans_virtio module) rdma connect to a specified RDMA channel + usbg connect to a specified usb gadget channel ======== ============================================ uname=name user name to attempt mount as on the remote server. The |