DSS usage

Ben Chan benchan at chromium.org
Thu Apr 10 09:17:52 PDT 2014

On Thu, Apr 10, 2014 at 9:07 AM, Aleksander Morgado <
aleksander at aleksander.es> wrote:

> On Thu, Apr 10, 2014 at 5:59 PM, Dan Williams <dcbw at redhat.com> wrote:
> >> Thanks Aleksander for the quick response.
> >> I tend to agree that DSS data should not be forwarded via VLAN
> interfaces as it's not a natural approach for such data pipes.
> >> Also userspace has to deal with bogus MAC address inserted by mbim
> driver.
> >>
> >> My request to handle this in userspace was based on fear that it would
> be much harder to integrate(or convince the vendors to integrate)
> modifications into usbnet and mbim kernel drivers.
> >> I'm afraid that it would take ages to hit the upstream kernel and
> finally the end distros.
> >>
> >> Of course as the long term solution a DSS channel should be visible as
> a character device.
> >
> > If there are known/quasi-standardized DSS protocols that eventually show
> > up, I think libmbim or something else should probably speak those
> > protocols too.  I guess we'll have to see how this all falls out when
> > DSS starts showing up (if it hasn't already?).
> I don't think that will ever happen. DSS is the 'standardized
> backdoor' that enables access to proprietary protocols to be used by
> vendors; think of firmware upgrades for the easiest case. My feeling
> is that from libmbim's perspective we'll always end up dealing with
> just channel creations and destructions, not with the actual DSS
> stream... :/
Yeah, a bit unfortunate but unavoidable reality is that you're likely to
find a DSS that just exposes an AT backdoor (I guess AT will survive until
the end of the universe).

The best we can do is try to establish (de facto) standards on common use
cases. I think USB/IF has a device firmware upgrade (DFU) standard, which
I'm not sure whether it's applicable for modem. But I don't see why there
can't be one standard interface. The implementation can still be different
on the modem internally.
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