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

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Message-ID: <4F049DEA.30506@suse.cz>
Date:	Wed, 04 Jan 2012 19:43:54 +0100
From:	Jiri Slaby <jslaby@...e.cz>
To:	Dave Jones <davej@...hat.com>,
	Linux Kernel <linux-kernel@...r.kernel.org>
Subject: Re: serial ports now asserting DTR and RTS during boot; breaks connected
 hardware

On 01/03/2012 05:13 PM, Dave Jones wrote:
> On Tue, Jan 03, 2012 at 05:00:45PM +0100, Jiri Slaby wrote:
>  > On 01/03/2012 04:37 PM, Dave Jones 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.
>  > 
>  > Hi!
>  > 
>  > I'm busy right now, however just after a quick look, it may be related to:
>  > https://lkml.org/lkml/2011/12/6/573
>  > 
>  > I'll take a look later.
> 
> thanks. I'll dig a little deeper. 
> 
>  > > 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 ? 
>  > 
>  > What changes do you mean? In serial-core.c? Thaat one is not used by USB
>  > serials. Hence this wouldn't occur with FTDI.
> 
> yeah, 303a7a1199c20f7c9452f024a6e17bf348b6b398 and c7d7abff40c27f82fe78b1091ab3fad69b2546f9
> jumped out at me, as they were they only things that changed DTR/RTS handling
> (at least mentioned in changelog) in recent times.

Rollback. The two commits are about uart. So they don't as well affect FTDI.

> The user mentions that it also affects 8250, though your point may mean
> that this is caused by something further up in the serial/tty code.

Or userspace. Try what Alan suggested. And ensure that FTDI is really
affected. Sometimes bug reporters do mistakes.

-- 
js
suse labs
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