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From: "Måns Rullgård" <mans@mansr.com>
To: "Bjørn Mork" <bjorn@mork.no>
Cc: Dan Williams <dcbw@redhat.com>, Johan Hovold <johan@kernel.org>,
	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
Date: Tue, 19 Mar 2019 16:26:39 +0000	[thread overview]
Message-ID: <yw1xmulqzv7k.fsf@mansr.com> (raw)
In-Reply-To: <878sxa9ag7.fsf@miraculix.mork.no> (=?iso-8859-1?Q?=22Bj=F8rn?= Mork"'s message of "Tue, 19 Mar 2019 15:59:36 +0100")

Bjørn Mork <bjorn@mork.no> writes:

> Måns Rullgård <mans@mansr.com> writes:
>> Dan Williams <dcbw@redhat.com> writes:
>>
>>> TLDR; some firmware uses the DTR signal as an indicator to come out of
>>> low-power mode. Without doing so you cannot talk to the modem over any
>>> of it's ports, QMI, net, or serial.
>>
>> I must be missing something, but how does a network interface have a DTR
>> signal?
>
> It does not.  But the network function is (ab)using the Comm class USB
> control message "SetControlLineState" to signal "wake up" from the host
> to the device.  Which is perfectly fine since the USB function in
> question is vendor specific.  The vendor can define any USB control
> message to mean anything they want. Reusing a Comm class message
> probably made sense to the firmware engineer designing this.  We can
> only note and adapt.
>
> It doesn't have anything to do with DTR.

Every time you think USB can't get any worse, it does.

-- 
Måns Rullgård

  reply	other threads:[~2019-03-19 16:26 UTC|newest]

Thread overview: 17+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2019-02-26 17:07 [PATCH] USB: serial: option: set driver_info for SIM5218 and compatibles Mans Rullgard
2019-02-27  8:33 ` Johan Hovold
2019-02-27 11:57   ` Måns Rullgård
2019-02-27 13:13     ` Johan Hovold
2019-02-27 14:32       ` Måns Rullgård
2019-03-18 14:32         ` Måns Rullgård
2019-03-19 10:28         ` Johan Hovold
2019-03-19 10:54           ` Måns Rullgård
2019-03-19 11:08             ` Johan Hovold
2019-03-19 12:25               ` Måns Rullgård
2019-03-19 12:27                 ` Johan Hovold
2019-03-19 12:43                   ` Johan Hovold
2019-03-19 14:30                     ` Dan Williams
2019-03-19 14:35                       ` Måns Rullgård
2019-03-19 14:59                         ` Bjørn Mork
2019-03-19 16:26                           ` Måns Rullgård [this message]
2019-03-19 17:15                             ` Bjørn Mork

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