usbip: move usbip_protocol.txt to Documentation

The usbip_protocol.txt, a document which describes usbip's
inner workings is currently located in the projects source
directory (drivers/usb/usbip/...). This patch moves it to
Documentation/usb.

This discussion was brought up by Guy Harris [0] during the
review of the USBIP dissector I wrote. For anyone interested:
support is available with the latest wireshark master/dev tree.
Simply select a packet from the usbip's tcp-stream you are
intrested on and select the USBIP as the protocol in the
"Decode As" dialog box [1].

Signed-off-by: Christian Lamparter <chunkeey@googlemail.com>

[0] <https://bugs.wireshark.org/bugzilla/show_bug.cgi?id=12127#c2>
[1] <https://www.wireshark.org/docs/wsug_html_chunked/ChCustProtocolDissectionSection.html#ChAdvDecodeAs>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

1 files changed, 358 insertions, 0 deletions

diff --git a/Documentation/usb/usbip_protocol.txt b/Documentation/usb/usbip_protocol.txt
new file mode 100644
index 000000000000..16b6fe27284c
--- /dev/null
+++ b/Documentation/usb/usbip_protocol.txt
@@ -0,0 +1,358 @@
+PRELIMINARY DRAFT, MAY CONTAIN MISTAKES!
+28 Jun 2011
+
+The USB/IP protocol follows a server/client architecture. The server exports the
+USB devices and the clients imports them. The device driver for the exported
+USB device runs on the client machine.
+
+The client may ask for the list of the exported USB devices. To get the list the
+client opens a TCP/IP connection towards the server, and sends an OP_REQ_DEVLIST
+packet on top of the TCP/IP connection (so the actual OP_REQ_DEVLIST may be sent
+in one or more pieces at the low level transport layer). The server sends back
+the OP_REP_DEVLIST packet which lists the exported USB devices. Finally the
+TCP/IP connection is closed.
+
+ virtual host controller                                 usb host
+      "client"                                           "server"
+  (imports USB devices)                             (exports USB devices)
+          |                                                 |
+          |                  OP_REQ_DEVLIST                 |
+          | ----------------------------------------------> |
+          |                                                 |
+          |                  OP_REP_DEVLIST                 |
+          | <---------------------------------------------- |
+          |                                                 |
+
+Once the client knows the list of exported USB devices it may decide to use one
+of them. First the client opens a TCP/IP connection towards the server and
+sends an OP_REQ_IMPORT packet. The server replies with OP_REP_IMPORT. If the
+import was successful the TCP/IP connection remains open and will be used
+to transfer the URB traffic between the client and the server. The client may
+send two types of packets: the USBIP_CMD_SUBMIT to submit an URB, and
+USBIP_CMD_UNLINK to unlink a previously submitted URB. The answers of the
+server may be USBIP_RET_SUBMIT and USBIP_RET_UNLINK respectively.
+
+ virtual host controller                                 usb host
+      "client"                                           "server"
+  (imports USB devices)                             (exports USB devices)
+          |                                                 |
+          |                  OP_REQ_IMPORT                  |
+          | ----------------------------------------------> |
+          |                                                 |
+          |                  OP_REP_IMPORT                  |
+          | <---------------------------------------------- |
+          |                                                 |
+          |                                                 |
+          |            USBIP_CMD_SUBMIT(seqnum = n)         |
+          | ----------------------------------------------> |
+          |                                                 |
+          |            USBIP_RET_SUBMIT(seqnum = n)         |
+          | <---------------------------------------------- |
+          |                        .                        |
+          |                        :                        |
+          |                                                 |
+          |            USBIP_CMD_SUBMIT(seqnum = m)         |
+          | ----------------------------------------------> |
+          |                                                 |
+          |            USBIP_CMD_SUBMIT(seqnum = m+1)       |
+          | ----------------------------------------------> |
+          |                                                 |
+          |            USBIP_CMD_SUBMIT(seqnum = m+2)       |
+          | ----------------------------------------------> |
+          |                                                 |
+          |            USBIP_RET_SUBMIT(seqnum = m)         |
+          | <---------------------------------------------- |
+          |                                                 |
+          |            USBIP_CMD_SUBMIT(seqnum = m+3)       |
+          | ----------------------------------------------> |
+          |                                                 |
+          |            USBIP_RET_SUBMIT(seqnum = m+1)       |
+          | <---------------------------------------------- |
+          |                                                 |
+          |            USBIP_CMD_SUBMIT(seqnum = m+4)       |
+          | ----------------------------------------------> |
+          |                                                 |
+          |            USBIP_RET_SUBMIT(seqnum = m+2)       |
+          | <---------------------------------------------- |
+          |                        .                        |
+          |                        :                        |
+          |                                                 |
+          |               USBIP_CMD_UNLINK                  |
+          | ----------------------------------------------> |
+          |                                                 |
+          |               USBIP_RET_UNLINK                  |
+          | <---------------------------------------------- |
+          |                                                 |
+
+The fields are in network (big endian) byte order meaning that the most significant
+byte (MSB) is stored at the lowest address.
+
+
+OP_REQ_DEVLIST: Retrieve the list of exported USB devices.
+
+ Offset    | Length | Value      | Description
+-----------+--------+------------+---------------------------------------------------
+ 0         | 2      | 0x0100     | Binary-coded decimal USBIP version number: v1.0.0
+-----------+--------+------------+---------------------------------------------------
+ 2         | 2      | 0x8005     | Command code: Retrieve the list of exported USB
+           |        |            |   devices.
+-----------+--------+------------+---------------------------------------------------
+ 4         | 4      | 0x00000000 | Status: unused, shall be set to 0
+
+OP_REP_DEVLIST: Reply with the list of exported USB devices.
+
+ Offset    | Length | Value      | Description
+-----------+--------+------------+---------------------------------------------------
+ 0         | 2      | 0x0100     | Binary-coded decimal USBIP version number: v1.0.0.
+-----------+--------+------------+---------------------------------------------------
+ 2         | 2      | 0x0005     | Reply code: The list of exported USB devices.
+-----------+--------+------------+---------------------------------------------------
+ 4         | 4      | 0x00000000 | Status: 0 for OK
+-----------+--------+------------+---------------------------------------------------
+ 8         | 4      | n          | Number of exported devices: 0 means no exported
+           |        |            |   devices.
+-----------+--------+------------+---------------------------------------------------
+ 0x0C      |        |            | From now on the exported n devices are described,
+           |        |            |   if any. If no devices are exported the message
+           |        |            |   ends with the previous "number of exported
+           |        |            |   devices" field.
+-----------+--------+------------+---------------------------------------------------
+           | 256    |            | path: Path of the device on the host exporting the
+           |        |            |   USB device, string closed with zero byte, e.g.
+           |        |            |   "/sys/devices/pci0000:00/0000:00:1d.1/usb3/3-2"
+           |        |            |   The unused bytes shall be filled with zero
+           |        |            |   bytes.
+-----------+--------+------------+---------------------------------------------------
+ 0x10C     | 32     |            | busid: Bus ID of the exported device, string
+           |        |            |   closed with zero byte, e.g. "3-2". The unused
+           |        |            |   bytes shall be filled with zero bytes.
+-----------+--------+------------+---------------------------------------------------
+ 0x12C     | 4      |            | busnum
+-----------+--------+------------+---------------------------------------------------
+ 0x130     | 4      |            | devnum
+-----------+--------+------------+---------------------------------------------------
+ 0x134     | 4      |            | speed
+-----------+--------+------------+---------------------------------------------------
+ 0x138     | 2      |            | idVendor
+-----------+--------+------------+---------------------------------------------------
+ 0x13A     | 2      |            | idProduct
+-----------+--------+------------+---------------------------------------------------
+ 0x13C     | 2      |            | bcdDevice
+-----------+--------+------------+---------------------------------------------------
+ 0x13E     | 1      |            | bDeviceClass
+-----------+--------+------------+---------------------------------------------------
+ 0x13F     | 1      |            | bDeviceSubClass
+-----------+--------+------------+---------------------------------------------------
+ 0x140     | 1      |            | bDeviceProtocol
+-----------+--------+------------+---------------------------------------------------
+ 0x141     | 1      |            | bConfigurationValue
+-----------+--------+------------+---------------------------------------------------
+ 0x142     | 1      |            | bNumConfigurations
+-----------+--------+------------+---------------------------------------------------
+ 0x143     | 1      |            | bNumInterfaces
+-----------+--------+------------+---------------------------------------------------
+ 0x144     |        | m_0        | From now on each interface is described, all
+           |        |            |   together bNumInterfaces times, with the
+           |        |            |   the following 4 fields:
+-----------+--------+------------+---------------------------------------------------
+           | 1      |            | bInterfaceClass
+-----------+--------+------------+---------------------------------------------------
+ 0x145     | 1      |            | bInterfaceSubClass
+-----------+--------+------------+---------------------------------------------------
+ 0x146     | 1      |            | bInterfaceProtocol
+-----------+--------+------------+---------------------------------------------------
+ 0x147     | 1      |            | padding byte for alignment, shall be set to zero
+-----------+--------+------------+---------------------------------------------------
+ 0xC +     |        |            | The second exported USB device starts at i=1
+ i*0x138 + |        |            | with the busid field.
+ m_(i-1)*4 |        |            |
+
+OP_REQ_IMPORT: Request to import (attach) a remote USB device.
+
+ Offset    | Length | Value      | Description
+-----------+--------+------------+---------------------------------------------------
+ 0         | 2      | 0x0100     | Binary-coded decimal USBIP version number: v1.0.0
+-----------+--------+------------+---------------------------------------------------
+ 2         | 2      | 0x8003     | Command code: import a remote USB device.
+-----------+--------+------------+---------------------------------------------------
+ 4         | 4      | 0x00000000 | Status: unused, shall be set to 0
+-----------+--------+------------+---------------------------------------------------
+ 8         | 32     |            | busid: the busid of the exported device on the
+           |        |            |   remote host. The possible values are taken
+           |        |            |   from the message field OP_REP_DEVLIST.busid.
+           |        |            |   A string closed with zero, the unused bytes
+           |        |            |   shall be filled with zeros.
+-----------+--------+------------+---------------------------------------------------
+
+OP_REP_IMPORT: Reply to import (attach) a remote USB device.
+
+ Offset    | Length | Value      | Description
+-----------+--------+------------+---------------------------------------------------
+ 0         | 2      | 0x0100     | Binary-coded decimal USBIP version number: v1.0.0
+-----------+--------+------------+---------------------------------------------------
+ 2         | 2      | 0x0003     | Reply code: Reply to import.
+-----------+--------+------------+---------------------------------------------------
+ 4         | 4      | 0x00000000 | Status: 0 for OK
+           |        |            |         1 for error
+-----------+--------+------------+---------------------------------------------------
+ 8         |        |            | From now on comes the details of the imported
+           |        |            |   device, if the previous status field was OK (0),
+           |        |            |   otherwise the reply ends with the status field.
+-----------+--------+------------+---------------------------------------------------
+           | 256    |            | path: Path of the device on the host exporting the
+           |        |            |   USB device, string closed with zero byte, e.g.
+           |        |            |   "/sys/devices/pci0000:00/0000:00:1d.1/usb3/3-2"
+           |        |            |   The unused bytes shall be filled with zero
+           |        |            |   bytes.
+-----------+--------+------------+---------------------------------------------------
+ 0x108     | 32     |            | busid: Bus ID of the exported device, string
+           |        |            |   closed with zero byte, e.g. "3-2". The unused
+           |        |            |   bytes shall be filled with zero bytes.
+-----------+--------+------------+---------------------------------------------------
+ 0x128     | 4      |            | busnum
+-----------+--------+------------+---------------------------------------------------
+ 0x12C     | 4      |            | devnum
+-----------+--------+------------+---------------------------------------------------
+ 0x130     | 4      |            | speed
+-----------+--------+------------+---------------------------------------------------
+ 0x134     | 2      |            | idVendor
+-----------+--------+------------+---------------------------------------------------
+ 0x136     | 2      |            | idProduct
+-----------+--------+------------+---------------------------------------------------
+ 0x138     | 2      |            | bcdDevice
+-----------+--------+------------+---------------------------------------------------
+ 0x139     | 1      |            | bDeviceClass
+-----------+--------+------------+---------------------------------------------------
+ 0x13A     | 1      |            | bDeviceSubClass
+-----------+--------+------------+---------------------------------------------------
+ 0x13B     | 1      |            | bDeviceProtocol
+-----------+--------+------------+---------------------------------------------------
+ 0x13C     | 1      |            | bConfigurationValue
+-----------+--------+------------+---------------------------------------------------
+ 0x13D     | 1      |            | bNumConfigurations
+-----------+--------+------------+---------------------------------------------------
+ 0x13E     | 1      |            | bNumInterfaces
+
+USBIP_CMD_SUBMIT: Submit an URB
+
+ Offset    | Length | Value      | Description
+-----------+--------+------------+---------------------------------------------------
+ 0         | 4      | 0x00000001 | command: Submit an URB
+-----------+--------+------------+---------------------------------------------------
+ 4         | 4      |            | seqnum: the sequence number of the URB to submit
+-----------+--------+------------+---------------------------------------------------
+ 8         | 4      |            | devid
+-----------+--------+------------+---------------------------------------------------
+ 0xC       | 4      |            | direction: 0: USBIP_DIR_OUT
+           |        |            |            1: USBIP_DIR_IN
+-----------+--------+------------+---------------------------------------------------
+ 0x10      | 4      |            | ep: endpoint number, possible values are: 0...15
+-----------+--------+------------+---------------------------------------------------
+ 0x14      | 4      |            | transfer_flags: possible values depend on the
+           |        |            |   URB transfer type, see below
+-----------+--------+------------+---------------------------------------------------
+ 0x18      | 4      |            | transfer_buffer_length
+-----------+--------+------------+---------------------------------------------------
+ 0x1C      | 4      |            | start_frame: specify the selected frame to
+           |        |            |   transmit an ISO frame, ignored if URB_ISO_ASAP
+           |        |            |   is specified at transfer_flags
+-----------+--------+------------+---------------------------------------------------
+ 0x20      | 4      |            | number_of_packets: number of ISO packets
+-----------+--------+------------+---------------------------------------------------
+ 0x24      | 4      |            | interval: maximum time for the request on the
+           |        |            |   server-side host controller
+-----------+--------+------------+---------------------------------------------------
+ 0x28      | 8      |            | setup: data bytes for USB setup, filled with
+           |        |            |   zeros if not used
+-----------+--------+------------+---------------------------------------------------
+ 0x30      |        |            | URB data. For ISO transfers the padding between
+           |        |            |   each ISO packets is not transmitted.
+
+
+  Allowed transfer_flags  | value      | control | interrupt | bulk     | isochronous
+ -------------------------+------------+---------+-----------+----------+-------------
+  URB_SHORT_NOT_OK        | 0x00000001 | only in | only in   | only in  | no
+  URB_ISO_ASAP            | 0x00000002 | no      | no        | no       | yes
+  URB_NO_TRANSFER_DMA_MAP | 0x00000004 | yes     | yes       | yes      | yes
+  URB_NO_FSBR             | 0x00000020 | yes     | no        | no       | no
+  URB_ZERO_PACKET         | 0x00000040 | no      | no        | only out | no
+  URB_NO_INTERRUPT        | 0x00000080 | yes     | yes       | yes      | yes
+  URB_FREE_BUFFER         | 0x00000100 | yes     | yes       | yes      | yes
+  URB_DIR_MASK            | 0x00000200 | yes     | yes       | yes      | yes
+
+
+USBIP_RET_SUBMIT: Reply for submitting an URB
+
+ Offset    | Length | Value      | Description
+-----------+--------+------------+---------------------------------------------------
+ 0         | 4      | 0x00000003 | command
+-----------+--------+------------+---------------------------------------------------
+ 4         | 4      |            | seqnum: URB sequence number
+-----------+--------+------------+---------------------------------------------------
+ 8         | 4      |            | devid
+-----------+--------+------------+---------------------------------------------------
+ 0xC       | 4      |            | direction: 0: USBIP_DIR_OUT
+           |        |            |            1: USBIP_DIR_IN
+-----------+--------+------------+---------------------------------------------------
+ 0x10      | 4      |            | ep: endpoint number
+-----------+--------+------------+---------------------------------------------------
+ 0x14      | 4      |            | status: zero for successful URB transaction,
+           |        |            |   otherwise some kind of error happened.
+-----------+--------+------------+---------------------------------------------------
+ 0x18      | 4      | n          | actual_length: number of URB data bytes
+-----------+--------+------------+---------------------------------------------------
+ 0x1C      | 4      |            | start_frame: for an ISO frame the actually
+           |        |            |   selected frame for transmit.
+-----------+--------+------------+---------------------------------------------------
+ 0x20      | 4      |            | number_of_packets
+-----------+--------+------------+---------------------------------------------------
+ 0x24      | 4      |            | error_count
+-----------+--------+------------+---------------------------------------------------
+ 0x28      | 8      |            | setup: data bytes for USB setup, filled with
+           |        |            |   zeros if not used
+-----------+--------+------------+---------------------------------------------------
+ 0x30      | n      |            | URB data bytes. For ISO transfers the padding
+           |        |            |   between each ISO packets is not transmitted.
+
+USBIP_CMD_UNLINK: Unlink an URB
+
+ Offset    | Length | Value      | Description
+-----------+--------+------------+---------------------------------------------------
+ 0         | 4      | 0x00000002 | command: URB unlink command
+-----------+--------+------------+---------------------------------------------------
+ 4         | 4      |            | seqnum: URB sequence number to unlink: FIXME: is this so?
+-----------+--------+------------+---------------------------------------------------
+ 8         | 4      |            | devid
+-----------+--------+------------+---------------------------------------------------
+ 0xC       | 4      |            | direction: 0: USBIP_DIR_OUT
+           |        |            |            1: USBIP_DIR_IN
+-----------+--------+------------+---------------------------------------------------
+ 0x10      | 4      |            | ep: endpoint number: zero
+-----------+--------+------------+---------------------------------------------------
+ 0x14      | 4      |            | seqnum: the URB sequence number given previously
+           |        |            |   at USBIP_CMD_SUBMIT.seqnum field
+-----------+--------+------------+---------------------------------------------------
+ 0x30      | n      |            | URB data bytes. For ISO transfers the padding
+           |        |            |   between each ISO packets is not transmitted.
+
+USBIP_RET_UNLINK: Reply for URB unlink
+
+ Offset    | Length | Value      | Description
+-----------+--------+------------+---------------------------------------------------
+ 0         | 4      | 0x00000004 | command: reply for the URB unlink command
+-----------+--------+------------+---------------------------------------------------
+ 4         | 4      |            | seqnum: the unlinked URB sequence number
+-----------+--------+------------+---------------------------------------------------
+ 8         | 4      |            | devid
+-----------+--------+------------+---------------------------------------------------
+ 0xC       | 4      |            | direction: 0: USBIP_DIR_OUT
+           |        |            |            1: USBIP_DIR_IN
+-----------+--------+------------+---------------------------------------------------
+ 0x10      | 4      |            | ep: endpoint number
+-----------+--------+------------+---------------------------------------------------
+ 0x14      | 4      |            | status: This is the value contained in the
+           |        |            |   urb->status in the URB completition handler.
+           |        |            |   FIXME: a better explanation needed.
+-----------+--------+------------+---------------------------------------------------
+ 0x30      | n      |            | URB data bytes. For ISO transfers the padding
+           |        |            |   between each ISO packets is not transmitted.