[systemd-devel] WebUSB

[Lars Knudsen]

I have som more input - but really need Reilly's comments on this:

As hardware manufacturers most often want to make it possible for users to
use their hardware in a WebUSB setting as well as in a "normal" app mode,
we will most likely see composite devices that could have the following
interfaces defined:

1. INT IF (for std CDC)
2. BULK CDC (non-webusb - e.g. for normal serial port bindings)
3. WebUSB CDC/bulk

In this case - ideally - the system should be allowed to grab 1 and 2 (but
most probably not modemmanager - as it's very unlikely that a modem will be
a webusb device.. as webusb devices assume internet) but leave 3 untouched
(unclaimed) for WebUSB bulk communication.  This means that the udev rules
need to be made on an interface level and not "blanket cover" the whole
device.

Beware that I might not be 100% correct on these assumptions and really
need some input on the intentions from Reilly or others with more knowledge
in the area (let's give California time to wake up :))

br
Lars


On Mon, Jan 9, 2017 at 11:29 AM, Aleksander Morgado <
aleksander at aleksander.es> wrote:

> On Mon, Jan 9, 2017 at 11:07 AM, Greg KH <greg at kroah.com> wrote:
> > 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, which will
> > prevent you from having to disconnect the driver from the device (and
> > the permissions issues involved in that.)
> >
> > Would that help out?
> >
> > And just do the same thing in modem manager, never grab a device with
> > this descriptor, and let the browser/webusb handle the control of the
> > device if it so desires.
>
> Not sure anything would be required in ModemManager if the kernel
> already skips the binding to cdc-acm; i.e. ModemManager won't do
> anything unless the TTY is exposed.
>
> --
> Aleksander
> https://aleksander.es
>
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