linux-kernel - Re: serial ports now asserting DTR and RTS during boot; breaks connected hardware

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Date:	Wed, 04 Jan 2012 21:54:29 +0100
From:	Jiri Slaby <jslaby@...e.cz>
To:	Alan Cox <alan@...rguk.ukuu.org.uk>
CC:	Dave Jones <davej@...hat.com>,
	Linux Kernel <linux-kernel@...r.kernel.org>,
	Jiri Slaby <jirislaby@...il.com>
Subject: Re: serial ports now asserting DTR and RTS during boot; breaks connected
 hardware

On 01/03/2012 05:06 PM, Alan Cox wrote:
> On Tue, 3 Jan 2012 10:37:07 -0500
> Dave Jones <davej@...hat.com> wrote:
> 
>> Jiri,
>> We got this report from a user who notes a change in behaviour for
>> his serial hardware over the last few kernel versions.
>>  
>> https://bugzilla.redhat.com/show_bug.cgi?id=771010
>>
>> This sounds like it might be related to your DTR/RTS changes back in March 2011 maybe ? 
> 
> Looks like your userspace to me at first glance.
> 
> ftdi_sio sets up the modem lines in set_termios. Set_termios is called
> from ftdi_open. ftdi_open is triggered by userspace.
> 
>>  > The following code in the ftdi_sio driver is one suspect but this behavior
>>  > happens on 8250 UARTs also so it is systemic now,
> 
> Likewise 8250 sets up the lines in serial8250_startup. This is called via
> uart_startup which is called via open.

Ok, let's apply the cut&paste rule. Does uninstalling ModemManager fix
the issue?

-- 
js
suse labs
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