Re: [PATCH, RFC] USBIP protocol documentation

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Matt Chen wrote:
> Hi Németh and Matt,
> We are also working on reviewing protocol here. We were wondering if
> you are available for letting us know which part you've already done.
> Then we can save the time for doing the same parts.

I've already sent everything I have. Nothing remained unsent from my side.

> And also we would like to follow your suggesting format to work on it.
> Then it would make it work much faster.
> Any suggestion ?
> 
> 2011/6/30 Németh Márton <nm127@xxxxxxxxxxx>
>> Matt Chen wrote:
>>> Hi Matt,
>>>
>>>
>>> 2011/6/30 matt mooney <mfm@xxxxxxxxxxxxx <mailto:mfm@xxxxxxxxxxxxx>>:
>>>> On 08:52 Tue 28 Jun     , N??meth M??rton wrote:
>>>>> From: M??rton N??meth <nm127@xxxxxxxxxxx <mailto:nm127@xxxxxxxxxxx>>
>>>>>
>>>>> USBIP v1.0.0 protocol documentation.
>>>>>
>>>>> Signed-off-by: M??rton N??meth <nm127@xxxxxxxxxxx
>>> <mailto:nm127@xxxxxxxxxxx>>
>>>>> ---
>>>>>
>>>>> Hi,
>>>>>
>>>>> I tried to document the USBIP protocol as implemented in the Linux
>>> kernel 3.0-rc2.
>>>> Yeah, thanks for doing this. I am also documenting the protocol but am not
>>>> finished yet. We can use yours as the base if you would like although
>>> I have a
>>>> few suggestions.
>>>>
>>>> For one, the grammar needs to be cleaned up, but instead of me
>>> pointing out all
>>>> of the needed corrections, I will send in a grammar corrections patch
>>> on top of
>> Please go on with the corrections. I really started documenting the
>> current USBIP protocol because I think digging in the source code is
>> not the right way to describe a protocol. I'm happy that the review
>> of the USBIP protocol description started. Once we have documented the current
>> USBIP protocol I think we'll see more clearly its weaknesses.
>>
>> What I think important to include in the protocol description is to
>> identify the unused fields and specify an exact value (usually zero) to
>> use for these fields. This makes possible future extension of the protocol
>> easy.
>>
>> One more random thing which came to my mind is that I tend to think that
>> the current implementation is buggy when ISO packets are transmitted.
>> I have a hama AC-150 webcam which is not working well with USBIP. This
>> webcam usually sends smaller ISO packets so there is a gap between
>> the ISO packets in one single URB. The problem came up already in case
>> of usbmon, see https://bugzilla.kernel.org/show_bug.cgi?id=22182 and
>> http://git.kernel.org/?p=linux/kernel/git/torvalds/linux-2.6.git;a=commit;h=b17ea167c5fb50dcd5dce5b874a467f04eec886d
>> .
>>
>>>> the finished document. I like that you did a time sequence diagram,
>>> which is
>>>> something I had neglected to include myself; however, I am not a big
>>> fan of how
>>>> you laid out the messages. I was planning on using packet diagrams.
>>> IMHO, it
>>>> makes understanding the message composition much easier allowing more
>>> insight to
>>>> be gathered from a cursory glance.
>>>>
>>>>
>>>>    Message Format
>>>>    --------------
>>>>         0               1               2               3
>>>>        +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
>>>>        |            Version            |            Opcode             |
>>>>        +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
>>>>        |                            Status                             |
>>>>        +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
>>>>        .                                                               .
>>>>        .                             Data                              .
>>>>        .                                                               .
>>>>        +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
>>>>
>>>>    Version: 16 bit
>>>>        Binary-coded decimal version number of the usbip-utils package from
>>>>        which the program was built.
>>>>
>>>>    Opcode: 16 bits
>>>>        ...
>>>>
>>> So as you mentioned, the message format is looked like below:
>>>
>>> OP_REQ_DEVLIST Message Format
>>>
>>>          0                 1               2
>>> 3                 4
>>>         +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
>>>         | 0000 0000 1000 0000 | 1000 0000 0000 0101 |
>>>         +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-
>>>         | 0000 0000 0000 0000   0000 0000 0000 0000 |
>>>         +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-
>>>
>>> Is this correct ?
>>>
>>> Personally, I like this way to describe the protocol.  ;-)
>> This layout format what is used in other RFCs, too, is really a better
>> way to show the messages. I think, however, that we don't need to put
>> the values in binary format, we could just put one hexadecimal number
>> in the gaps, like this:
>>
>>  OP_REQ_DEVLIST Message Format
>>
>>
>>     0               1               2               3
>>    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
>>    |            0x0100             |            0x8005             |
>>    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
>>    |                          0x00000000                           |
>>    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
>>
>>>> As you may or may not see, I was going to take a more generic approach
>>> and then
>>>> describe the fields on a per-op basis. Of course, the main point here
>>> is that
>>>> the protocol is documented, so I am not opposed to a different style
>>> being used.
>>>> But if you insist on the current layout, do not put a value for the
>>> version
>>>> because it is not constant (and in fact no longer at 1.0.0). And the
>>> "Meaning"
>>>> header should be "Description" or something better.
>>>>
>>>> Hmm, taking another look the layout just seems to busy... I really do
>>> think we
>>>> should find a different way to format the information.
>>>>
>>>> Thanks,
>>>> matt
>>>>
>>>>> The description is a preliminary draft only, it may contain mistakes.
>>> I tried
>>>>> to document what I have understand from the source code and from the
>>> actual
>>>>> captured network traffic when the USBIP is in action. Please review
>>> it, correct it,
>>>>> point out the missing parts.
>>>>>
>>>>> During I have documented the protocol a question came into my mind:
>>> why do we
>>>>> have two different type of package when the URB completition handler
>>> is called,
>>>>> namely USB_RET_SUBMIT and USBIP_RET_UNLINK? As far as I can see this
>>> causes race
>>>>> condition because for one URB the completition handler is only called
>>> once. If
>>>>> the one URB is sent in with USB_CMD_SUBMIT and then unlinked with
>>> USB_CMD_UNLINK
>>>>> the completition handler is called only once. In the protocol,
>>> however, we have
>>>>> two different type of packets: USB_RET_SUBMIT and USBIP_RET_UNLINK.
>>> The status
>>>>> field of these messages may contain anything in this case depending
>>> on the timing.
>>>>> Regards,
>>>>>
>>>>>       M??rton N??meth
>>>>> ---
>>>>> diff -uprN staging-2.6.orig/drivers/staging/usbip/usbip_protocol.txt
>>> staging-2.6/drivers/staging/usbip/usbip_protocol.txt
>>>>> --- staging-2.6.orig/drivers/staging/usbip/usbip_protocol.txt
>>> 1970-01-01 01:00:00.000000000 +0100
>>>>> +++ staging-2.6/drivers/staging/usbip/usbip_protocol.txt
>>>  2011-06-28 08:30:04.000000000 +0200
>>>>> @@ -0,0 +1,352 @@
>>>>> +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 trasfer 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      | Meaning
>>>>>
>>> +-----------+--------+------------+---------------------------------------------------
>>>>> + 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      | Meaning
>>>>>
>>> +-----------+--------+------------+---------------------------------------------------
>>>>> + 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      | Meaning
>>>>>
>>> +-----------+--------+------------+---------------------------------------------------
>>>>> + 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      | Meaning
>>>>>
>>> +-----------+--------+------------+---------------------------------------------------
>>>>> + 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      | Meaning
>>>>>
>>> +-----------+--------+------------+---------------------------------------------------
>>>>> + 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_IN
>>>>> +           |        |            |            1: USBIP_DIR_OUT
>>>>>
>>> +-----------+--------+------------+---------------------------------------------------
>>>>> + 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      | Meaning
>>>>>
>>> +-----------+--------+------------+---------------------------------------------------
>>>>> + 0         | 4      | 0x00000002 | command
>>>>>
>>> +-----------+--------+------------+---------------------------------------------------
>>>>> + 4         | 4      |            | seqnum: URB sequence number
>>>>>
>>> +-----------+--------+------------+---------------------------------------------------
>>>>> + 8         | 4      |            | devid
>>>>>
>>> +-----------+--------+------------+---------------------------------------------------
>>>>> + 0xC       | 4      |            | direction: 0: USBIP_DIR_IN
>>>>> +           |        |            |            1: USBIP_DIR_OUT
>>>>>
>>> +-----------+--------+------------+---------------------------------------------------
>>>>> + 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      | Meaning
>>>>>
>>> +-----------+--------+------------+---------------------------------------------------
>>>>> + 0         | 4      | 0x00000003 | 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_IN
>>>>> +           |        |            |            1: USBIP_DIR_OUT
>>>>>
>>> +-----------+--------+------------+---------------------------------------------------
>>>>> + 0x10      | 4      |            | ep: endpoint number: zero
>>>>>
>>> +-----------+--------+------------+---------------------------------------------------
>>>>> + 0x14      | 4      |            | seqnum: the URB sequence number
>>> given previously
>>>>> +           |        |            |   at USBIP_CMD_SUBMIT.seqnum field
>>>>> +
>>>>> +USBIP_RET_UNLINK: Reply for URB unlink
>>>>> +
>>>>> + Offset    | Length | Value      | Meaning
>>>>>
>>> +-----------+--------+------------+---------------------------------------------------
>>>>> + 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_IN
>>>>> +           |        |            |            1: USBIP_DIR_OUT
>>>>>
>>> +-----------+--------+------------+---------------------------------------------------
>>>>> + 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.
>>>>>
>>>> _______________________________________________
>>>> devel mailing list
>>>> devel@xxxxxxxxxxxxxxxxxxxxxx <mailto:devel@xxxxxxxxxxxxxxxxxxxxxx>
>>>> http://driverdev.linuxdriverproject.org/mailman/listinfo/devel
>>>>
>>>
>>>
>>> --
>>> Thanks ~
>>> Matt Chen
>>>
>>>
>>>
> 
> 
> 
> --
> Thanks ~
> Matt Chen
> 
> 

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