linux-kernel - Re: [PATCH] USB: serial: option: set driver

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Message-ID: <yw1x8sxb125q.fsf@mansr.com>
Date:   Tue, 19 Mar 2019 12:25:53 +0000
From:   Måns Rullgård <mans@...sr.com>
To:     Johan Hovold <johan@...nel.org>
Cc:     Bjørn Mork <bjorn@...k.no>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        linux-usb@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] USB: serial: option: set driver_info for SIM5218 and compatibles

Johan Hovold <johan@...nel.org> writes:

> On Tue, Mar 19, 2019 at 10:54:00AM +0000, Måns Rullgård wrote:
>> Johan Hovold <johan@...nel.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).

-- 
Måns Rullgård