netdev - Re: cellular modem driver APIs

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Message-ID: <CAGRyCJHtfVj+6P-cMaBc4=Di8NPOzdSiVGcU12+S2tDs5_AdJQ@mail.gmail.com>
Date:   Sat, 6 Apr 2019 19:20:04 +0200
From:   Daniele Palmas <dnlplm@...il.com>
To:     Johannes Berg <johannes@...solutions.net>
Cc:     Bjørn Mork <bjorn@...k.no>,
        netdev@...r.kernel.org, Dan Williams <dcbw@...hat.com>,
        Subash Abhinov Kasiviswanathan <subashab@...eaurora.org>,
        Sean Tranchetti <stranche@...eaurora.org>,
        Aleksander Morgado <aleksander@...ksander.es>
Subject: Re: cellular modem driver APIs

Hi,

Il giorno gio 4 apr 2019 alle ore 11:00 Johannes Berg
<johannes@...solutions.net> ha scritto:

> > >   (2) Channels are created using sysfs (qmi_wwan)
> > >
> > >       This feels almost worse - channels are created using sysfs and
> > >       just *bam* new netdev shows up, no networking APIs are used to
> > >       create them at all, and I suppose you can't even query the channel
> > >       ID for each netdev if you rename them or so. Actually, maybe you
> > >       can in sysfs, not sure I understand the code fully.
> >
> > This time I was, and I tried to learn from the MBIM mistake. So I asked
> > the users (ModemManager developers++), proposing a netlink API as a
> > possible solution:
> >
> > https://lists.freedesktop.org/archives/libqmi-devel/2017-January/001900.html
> >
> > The options I presented were those I saw at the time: VLANs like
> > cdc_mbim, a new netlink API, or sysfs.  There wasn't much feedback, but
> > sysfs "won".  So this was a decision made by the users of the API, FWIW.
>
> Fair point. Dan pointed out that no (default) userspace actually exists
> to do this though, and users kinda of have to do it manually - he says
> modem manager and libmbim all just use the default channel today. So not
> sure they really went on to become users of this ;-)
>

the qmi_wwan sysfs qmap feature, being very easy to use, is serving
well for me and customers of the company I work for (mainly directly
with libqmi, not ModemManager), but I understand the need to have a
common framework and will gladly test and provide feedback for any new
development related to this.

Regards,
Daniele

>
> johannes
>