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Date:   Tue, 19 Mar 2019 13:27:19 +0100
From:   Johan Hovold <johan@kernel.org>
To:     =?iso-8859-1?Q?M=E5ns_Rullg=E5rd?= <mans@mansr.com>
Cc:     Johan Hovold <johan@kernel.org>,
        =?iso-8859-1?Q?Bj=F8rn?= Mork <bjorn@mork.no>,
        Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
        linux-usb@vger.kernel.org, linux-kernel@vger.kernel.org
Subject: Re: [PATCH] USB: serial: option: set driver_info for SIM5218 and
 compatibles
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On Tue, Mar 19, 2019 at 12:25:53PM +0000, M?ns Rullg?rd wrote:
> Johan Hovold <johan@kernel.org> writes:
> 
> > On Tue, Mar 19, 2019 at 10:54:00AM +0000, M?ns Rullg?rd wrote:
> >> Johan Hovold <johan@kernel.org> writes:
> >
> >> >> Regardless, setting the NCTRL flag should be harmless.
> >> >
> >> > Well, there are devices that depend on getting these requests, at least
> >> > for the QMI interface. But we can always revert if anyone complains.
> >> 
> >> The QMI interface doesn't even pretend to be a uart.  The other ones do,
> >> but there isn't actually any real uart behind them.  For instance, it
> >> doesn't matter what baud rate one sets.
> >
> > Sure, but some devices still require "DTR" to be set for the QMI
> > interface, so there not being any real uart is no guarantee that there
> > is no firmware that expects these calls.
> 
> Now I'm thoroughly confused.  The QMI interface has a completely
> separate driver that creates a network device (if I'm reading the code
> correctly).

I was just giving an example of firmware sometimes doing unexpected
things.

Johan