netdev - Re: [PATCH net-next] qmi_wwan: unconditionally reject 2 ep interfaces

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Date:   Tue, 11 Feb 2020 12:04:23 +0100
From:   Kristian Evensen <kristian.evensen@...il.com>
To:     Bjørn Mork <bjorn@...k.no>
Cc:     Network Development <netdev@...r.kernel.org>,
        linux-usb@...r.kernel.org,
        Aleksander Morgado <aleksander@...ksander.es>
Subject: Re: [PATCH net-next] qmi_wwan: unconditionally reject 2 ep interfaces

Hi Bjørn,

On Sat, Feb 8, 2020 at 4:55 PM Bjørn Mork <bjorn@...k.no> wrote:
>
> We have been using the fact that the QMI and DIAG functions
> usually are the only ones with class/subclass/protocol being
> ff/ff/ff on Quectel modems. This has allowed us to match the
> QMI function without knowing the exact interface number,
> which can vary depending on firmware configuration.
>
> The ability to silently reject the DIAG function, which is
> usually handled by the option driver, is important for this
> method to work.  This is done based on the knowledge that it
> has exactly 2 bulk endpoints.  QMI function control interfaces
> will have either 3 or 1 endpoint. This rule is universal so
> the quirk condition can be removed.
>
> The fixed layouts known from the Gobi1k and Gobi2k modems
> have been gradually replaced by more dynamic layouts, and
> many vendors now use configurable layouts without changing
> device IDs.  Renaming the class/subclass/protocol matching
> macro makes it more obvious that this is now not Quectel
> specific anymore.
>
> Cc: Kristian Evensen <kristian.evensen@...il.com>
> Cc: Aleksander Morgado <aleksander@...ksander.es>
> Signed-off-by: Bjørn Mork <bjorn@...k.no>
> ---
> What do you think, Kristian?  There is no real need to limit this
> rule to Quectel modems, is there?  And from what I've understood,
> it seems that most/all the upcoming X55 modems will have a
> completely configurable layout.  Which means that we should
> avoid macthing on interface number if we can.  And I believe we
> can. I've not yet seen an example where ff/ff/ff would match
> anything except QMI and DIAG.

I am sorry for my late reply, your email had for some reason ended up
in my spam filter. I agree with you reasoning and I think that making
the Quectel-code generic is a good idea. I went through the modem I
have, and could also not find any modems where the current
Quectel-code would incorrectly match. FWIW:

Acked-by: Kristian Evensen <kristian.evensen@...il.com>

BR,
Kristian