linux-kernel - Re: Is it ok if ModemManager process is killed AFTER network-interface is brought up and IP-Address assigned?

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Message-ID: <CAHP4M8Wqf3-eYxbXmciwto1teCQB+rNK74LgKJTNQan9hH1cHw@mail.gmail.com>
Date:	Wed, 10 Aug 2016 10:00:09 +0530
From:	Ajay Garg <ajaygargnsit@...il.com>
To:	Greg KH <gregkh@...uxfoundation.org>
Cc:	linux-kernel@...r.kernel.org, linux-usb@...r.kernel.org
Subject: Re: Is it ok if ModemManager process is killed AFTER
 network-interface is brought up and IP-Address assigned?

Ok Greg :)

On Tue, Aug 9, 2016 at 1:44 PM, Greg KH <gregkh@...uxfoundation.org> wrote:
> On Tue, Aug 09, 2016 at 12:48:12PM +0530, Ajay Garg wrote:
>> Hi All.
>>
>> We are using Sierra's USB-to-WWAN driver on Ubuntu-14 for Sierra's
>> MC8090 modem, and we have a requirement wherein we need to have access
>> to the modem-serial-port (from our user-application that is).
>>
>> Right now, we see that /usr/sbin/ModemManager is always connected to
>> /dev/ttyUSB3 (which means we cannot connect to the port from our
>> application at the same time, or even if we can, received-data will be
>> at best inconsistent).
>>
>>
>> We are thinking of the following ::
>>
>> * Initially, let nmcli and ModemManager do their work, and let them
>> bring the WWAN interface up.
>>
>> * Once this happens, we permanently-down the ModemManager from our
>> application-binary, thereby freeing up /dev/ttyUSB3.
>>
>> * Thereafter, we are free to connect to /dev/ttyUSB3 from our
>> application, thereby using features like SMS-notification (+CMTI),
>> signal-strength (+CSQ), etc.
>>
>>
>>
>> Does our approach make sense?
>> We will be grateful to any help.
>
> Why not ask the modem manager team about this?  The kernel doesn't care
> what you do with the device links :)
>
> thanks,
>
> greg k-h



-- 
Regards,
Ajay