[systemd-devel] WebUSB

Lars Knudsen larsgk at gmail.com
Mon Jan 9 23:11:16 UTC 2017


I finally managed to make a configuration that *seems* to work and I
realize that I may have had something else blocking the WebUSB interface
(2) while modemmanager was communicating with the CDC_ACM interface (1).

I made a clean arbitrary VID/PID and get what seems to be a functioning
WebUSB (now) while modemmanager sends "AT...AT..." to the CDC interface -
so while I thought the modemmanager grabbed my WebUSB interface part, it
must have been because of a faulty combination on my side - my apologies.
WebUSB actually *does* seem to give immediate "bulk" access to a device
otherwise claimed by modemmanager - a very nice option to have and sorry
for the confusion I had that modemmanager grabbed more interfaces than it
should have.

Still, the original request still stands and please tell me if it's a
viable path:

1.  If a device has a WebUSB descriptor, it's most probably *not* a modem -
and should in stead be considered a device that in this rare case needs to
be whitelisted (as modem), while defaulting to not being it.  This is to
ease the usage from non-browsers to the same hardware, which can then
happen immediately and not be required to fail and wait over the
modemmanager probing period (30 sec?) - related to modemmanager
2. If a device has a WebUSB descriptor, at least the interface linked to
WebUSB should be made accessible in user land by default so no average user
has to figure out how to do udev rules - related to udev/systemd

my headers that seem to work now for the case above:

Bus 002 Device 089: ID 1209:d010 InterBiometrics
Device Descriptor:
  bLength                18
  bDescriptorType         1
  bcdUSB               2.10
  bDeviceClass            0 (Defined at Interface level)
  bDeviceSubClass         0
  bDeviceProtocol         0
  bMaxPacketSize0        64
  idVendor           0x1209 InterBiometrics
  idProduct          0xd010
  bcdDevice            0.01
  iManufacturer           1 empriKit
  iProduct                2 empriKit|MOTION
  iSerial                 3 00.01
  bNumConfigurations      1
  Configuration Descriptor:
    bLength                 9
    bDescriptorType         2
    wTotalLength           90
    bNumInterfaces          3
    bConfigurationValue     1
    iConfiguration          0
    bmAttributes         0xc0
      Self Powered
    MaxPower              100mA
    Interface Descriptor:
      bLength                 9
      bDescriptorType         4
      bInterfaceNumber        0
      bAlternateSetting       0
      bNumEndpoints           1
      bInterfaceClass         2 Communications
      bInterfaceSubClass      2 Abstract (modem)
      bInterfaceProtocol      1 AT-commands (v.25ter)
      iInterface              0
      CDC Header:
        bcdCDC               1.10
      CDC Call Management:
        bmCapabilities       0x03
          call management
          use DataInterface
        bDataInterface          1
      CDC ACM:
        bmCapabilities       0x02
          line coding and serial state
      CDC Union:
        bMasterInterface        0
        bSlaveInterface         1
      Endpoint Descriptor:
        bLength                 7
        bDescriptorType         5
        bEndpointAddress     0x81  EP 1 IN
        bmAttributes            3
          Transfer Type            Interrupt
          Synch Type               None
          Usage Type               Data
        wMaxPacketSize     0x0010  1x 16 bytes
        bInterval              16
    Interface Descriptor:
      bLength                 9
      bDescriptorType         4
      bInterfaceNumber        1
      bAlternateSetting       0
      bNumEndpoints           2
      bInterfaceClass        10 CDC Data
      bInterfaceSubClass      0 Unused
      bInterfaceProtocol      0
      iInterface              0
      Endpoint Descriptor:
        bLength                 7
        bDescriptorType         5
        bEndpointAddress     0x82  EP 2 IN
        bmAttributes            2
          Transfer Type            Bulk
          Synch Type               None
          Usage Type               Data
        wMaxPacketSize     0x0040  1x 64 bytes
        bInterval               0
      Endpoint Descriptor:
        bLength                 7
        bDescriptorType         5
        bEndpointAddress     0x02  EP 2 OUT
        bmAttributes            2
          Transfer Type            Bulk
          Synch Type               None
          Usage Type               Data
        wMaxPacketSize     0x0040  1x 64 bytes
        bInterval               0
    Interface Descriptor:
      bLength                 9
      bDescriptorType         4
      bInterfaceNumber        2
      bAlternateSetting       0
      bNumEndpoints           2
      bInterfaceClass       255 Vendor Specific Class
      bInterfaceSubClass      0
      bInterfaceProtocol      0
      iInterface              0
      Endpoint Descriptor:
        bLength                 7
        bDescriptorType         5
        bEndpointAddress     0x85  EP 5 IN
        bmAttributes            2
          Transfer Type            Bulk
          Synch Type               None
          Usage Type               Data
        wMaxPacketSize     0x0040  1x 64 bytes
        bInterval               0
      Endpoint Descriptor:
        bLength                 7
        bDescriptorType         5
        bEndpointAddress     0x05  EP 5 OUT
        bmAttributes            2
          Transfer Type            Bulk
          Synch Type               None
          Usage Type               Data
        wMaxPacketSize     0x0040  1x 64 bytes
        bInterval               0
Binary Object Store Descriptor:
  bLength                 5
  bDescriptorType        15
  wTotalLength           29
  bNumDeviceCaps          1
  ** UNRECOGNIZED:  18 10 05 00 38 b6 08 34 a9 09 a0 47 8b fd a0 76 88 15
b6 65 00 01 57 02
Device Status:     0x0001
  Self Powered


On Mon, Jan 9, 2017 at 10:32 PM, Reilly Grant <me at reilly.io> wrote:

> On 2017-01-09 9:55 am, Greg KH wrote:
>
>> On Mon, Jan 09, 2017 at 06:13:04PM +0100, Bjørn Mork wrote:
>>
>>> Greg KH <greg at kroah.com> writes:
>>> > On Mon, Jan 09, 2017 at 09:40:59AM +0000, Kenneth Rohde Christiansen
>>> wrote:
>>> >> Web USB can only grab devices which has special Web USB headers. It
>>> can not
>>> >> grab any USB device.
>>> >>
>>> >> https://wicg.github.io/webusb/#webusb-descriptors
>>> >
>>> > Ah, fun :(
>>> >
>>> > So, we can add a quirk into the kernel cdc-acm driver to never bind to
>>> a
>>> > device that has the wusb platform capability descriptor,
>>>
>>> I fail to see why a quirk should be necessary. New device classes are
>>> expected to use new class/subclass codes distintly different from
>>> anything handled by existing class drivers.
>>>
>>
>> One would hope, but it seems like they want to piggy-back on the cdc-acm
>> spec.  But I could be totally wrong here, does anyone have the actual
>> descriptor dump of a device anywhere?
>>
>
> We don't want to piggy-back on the CDC-ACM spec. A WebUSB device should
> always have its interfaces marked vendor-specific. Below is an example of a
> device which implements both a CDC-ACM interface and a WebUSB interface. As
> far as I've noticed ModemManager has not interfered with the browser
> accessing this device but Lars has observed this behavior. What I have had
> to do, however, is add a udev rule which sets ownership on the devnode so
> that the browser can access it as an unprivileged user-space application.
> What would be nice to have from systemd-udevd is a way to write a rule that
> will detect the presence of WebUSB descriptors (which is a BOS capability
> descriptor) and set ownership accordingly.
>
> Bus 002 Device 040: ID 2341:8037 Arduino SA
> Device Descriptor:
>   bLength                18
>   bDescriptorType         1
>   bcdUSB               2.10
>   bDeviceClass            0 (Defined at Interface level)
>   bDeviceSubClass         0
>   bDeviceProtocol         0
>   bMaxPacketSize0        64
>   idVendor           0x2341 Arduino SA
>   idProduct          0x8037
>   bcdDevice            1.00
>   iManufacturer           1 Arduino LLC
>   iProduct                2 Arduino Micro
>   iSerial                 3 WUARTR
>   bNumConfigurations      1
>   Configuration Descriptor:
>     bLength                 9
>     bDescriptorType         2
>     wTotalLength           98
>     bNumInterfaces          3
>     bConfigurationValue     1
>     iConfiguration          0
>     bmAttributes         0xa0
>       (Bus Powered)
>       Remote Wakeup
>     MaxPower              500mA
>     Interface Association:
>       bLength                 8
>       bDescriptorType        11
>       bFirstInterface         0
>       bInterfaceCount         2
>       bFunctionClass          2 Communications
>       bFunctionSubClass       2 Abstract (modem)
>       bFunctionProtocol       1 AT-commands (v.25ter)
>       iFunction               0
>     Interface Descriptor:
>       bLength                 9
>       bDescriptorType         4
>       bInterfaceNumber        0
>       bAlternateSetting       0
>       bNumEndpoints           1
>       bInterfaceClass         2 Communications
>       bInterfaceSubClass      2 Abstract (modem)
>       bInterfaceProtocol      0 None
>       iInterface              0
>       CDC Header:
>         bcdCDC               1.10
>       CDC Call Management:
>         bmCapabilities       0x01
>           call management
>         bDataInterface          1
>       CDC ACM:
>         bmCapabilities       0x06
>           sends break
>           line coding and serial state
>       CDC Union:
>         bMasterInterface        0
>         bSlaveInterface         1
>       Endpoint Descriptor:
>         bLength                 7
>         bDescriptorType         5
>         bEndpointAddress     0x81  EP 1 IN
>         bmAttributes            3
>           Transfer Type            Interrupt
>           Synch Type               None
>           Usage Type               Data
>         wMaxPacketSize     0x0010  1x 16 bytes
>         bInterval              64
>     Interface Descriptor:
>       bLength                 9
>       bDescriptorType         4
>       bInterfaceNumber        1
>       bAlternateSetting       0
>       bNumEndpoints           2
>       bInterfaceClass        10 CDC Data
>       bInterfaceSubClass      0 Unused
>       bInterfaceProtocol      0
>       iInterface              0
>       Endpoint Descriptor:
>         bLength                 7
>         bDescriptorType         5
>         bEndpointAddress     0x02  EP 2 OUT
>         bmAttributes            2
>           Transfer Type            Bulk
>           Synch Type               None
>           Usage Type               Data
>         wMaxPacketSize     0x0040  1x 64 bytes
>         bInterval               0
>       Endpoint Descriptor:
>         bLength                 7
>         bDescriptorType         5
>         bEndpointAddress     0x83  EP 3 IN
>         bmAttributes            2
>           Transfer Type            Bulk
>           Synch Type               None
>           Usage Type               Data
>         wMaxPacketSize     0x0040  1x 64 bytes
>         bInterval               0
>     Interface Descriptor:
>       bLength                 9
>       bDescriptorType         4
>       bInterfaceNumber        2
>       bAlternateSetting       0
>       bNumEndpoints           2
>       bInterfaceClass       255 Vendor Specific Class
>       bInterfaceSubClass      0
>       bInterfaceProtocol      0
>       iInterface              0
>       Endpoint Descriptor:
>         bLength                 7
>         bDescriptorType         5
>         bEndpointAddress     0x04  EP 4 OUT
>         bmAttributes            2
>           Transfer Type            Bulk
>           Synch Type               None
>           Usage Type               Data
>         wMaxPacketSize     0x0040  1x 64 bytes
>         bInterval               0
>       Endpoint Descriptor:
>         bLength                 7
>         bDescriptorType         5
>         bEndpointAddress     0x85  EP 5 IN
>         bmAttributes            2
>           Transfer Type            Bulk
>           Synch Type               None
>           Usage Type               Data
>         wMaxPacketSize     0x0040  1x 64 bytes
>         bInterval               0
> Binary Object Store Descriptor:
>   bLength                 5
>   bDescriptorType        15
>   wTotalLength           57
>   bNumDeviceCaps          2
> FIXME: alloc bigger buffer for device capability descriptors
> Device Status:     0x0000
>   (Bus Powered)
>
>
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