linux-kernel - Re: [PATCH] option: Improve Quectel EP06 detection

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Message-ID: <20180913091753.GA3443@localhost>
Date:   Thu, 13 Sep 2018 11:17:53 +0200
From:   Johan Hovold <johan@...nel.org>
To:     Bjørn Mork <bjorn@...k.no>
Cc:     Dan Williams <dcbw@...hat.com>, Lars Melin <larsm17@...il.com>,
        Kristian Evensen <kristian.evensen@...il.com>,
        Johan Hovold <johan@...nel.org>, linux-usb@...r.kernel.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH] option: Improve Quectel EP06 detection

On Wed, Sep 12, 2018 at 10:34:43PM +0200, Bjørn Mork wrote:
> Dan Williams <dcbw@...hat.com> writes:
> 
> > The fact that the firmware implementation has the ability to change the
> > endpoints is unrelated to Kristian's case, and that alone is
> > justification for this to be quirked in the driver.  People other than
> > Kristian will undoubtedly use the functionality, on platforms less
> > limited.
> 
> FWIW, I agree with Dan and Kristian on this. It's a documented feature,
> and it will be used. The reasons are irrelevant. The firmware
> implementation is inconvenient, but we should still strive to make it
> Just Work in Linux.  Kristian's solution does that.
>
> > Also most Huawei modems have the ability to change their layout and
> > configuration just like the EP06 via the U2DIAG and SETPORT commands.
> 
> Yes, but they are nice enough to use unique class/subclass/protocol
> triplets for their functions so it's easy to support the changing
> layout.  At least as long as they use their own VID and not some laptop
> vendor's..
> 
> The Sierra Wireless strategy, using fixed interface numbers leaving
> "holes" is another fine solution to the problem.  Or they could have
> allocated unique VIDs per function combination, as long as the number of
> valid combinations are low.  But they didn't.  It's not like it's the
> first bad firmware design we've had to deal with.  Let's just work
> around it, like we always do.  No need to make life difficult for end
> users just because Quectel makes life difficult for us.

Ok, thanks for everyone for your input. As Lars I was sceptical about
this, but if this is contained to Quectel and we have a solutions which
hopefully covers all permutations for their other devices, let's go
along with this.

I'd prefer seeing this contained in the device-id table as far as
possible rather than maintaining a second table of product ids in
probe() so I've cooked up a patch (on top of this one) adding a new
device-id match flag.

Kristian would you mind giving it a try? 

Oh, also note that I dropped the RSVD(5) for the ADB interface in your
patch since it uses a different subclass anyway. I'll submit both
patches in a series.

Thanks,
Johan