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