netdev - Re: cellular modem APIs

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Message-ID: <8b6b6174-7de4-b9a9-242b-765da647402e@gmail.com>
Date:   Wed, 29 May 2019 15:44:12 -0500
From:   Denis Kenzior <denkenz@...il.com>
To:     Johannes Berg <johannes@...solutions.net>,
        Marcel Holtmann <marcel@...tmann.org>
Cc:     netdev@...r.kernel.org, linux-wireless@...r.kernel.org,
        Subash Abhinov Kasiviswanathan <subashab@...eaurora.org>,
        Dan Williams <dcbw@...hat.com>,
        Sean Tranchetti <stranche@...eaurora.org>,
        Daniele Palmas <dnlplm@...il.com>,
        Aleksander Morgado <aleksander@...ksander.es>,
        Bjørn Mork <bjorn@...k.no>
Subject: Re: cellular modem APIs - take 2

Hi Johannes,

> 
> After all, I'm not really proposing that we put oFono or something like
> it into the kernel - far from it! I'm only proposing that we kill the
> many various ways of creating and managing the necessary netdevs (VLANs,
> sysfs, rmnet, ...) from a piece of software like oFono (or libmbim or
> whatever else).

I do like the concept of unifying this if possible.  The question is, is 
it actually possible :)  I think Dan covered most of the aspects of what 
userspace has to deal with already.  But the basic issue is that there's 
a heck of a lot of different ways of doing it.

> 
> Apart from CAIF and phonet, oFono doesn't even try to do this though,
> afaict, so I guess it relies on the default netdev created, or some out-
> of-band configuration is still needed?

Actually it can.  We can drive modems which provide only a single serial 
port and run multiplexing over that.  So we fully control the number of 
control channels created, the number of netdevs created and even 
create/destroy them on as needed basis.  And these netdevs can be PPP 
encapsulated or pure IP or whatever else.

Regards,
-Denis