From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1757294Ab0FTUzK (ORCPT ); Sun, 20 Jun 2010 16:55:10 -0400 Received: from moutng.kundenserver.de ([212.227.17.8]:57836 "EHLO moutng.kundenserver.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1757079Ab0FTUzF (ORCPT ); Sun, 20 Jun 2010 16:55:05 -0400 From: Arnd Bergmann To: Alan Cox Subject: Re: [PATCH] serial: revert "Use block_til_ready helper" Date: Sun, 20 Jun 2010 22:54:34 +0200 User-Agent: KMail/1.13.2 (Linux/2.6.35-rc3-00053-g34ffc96; KDE/4.4.2; x86_64; ; ) Cc: Tony Luck , Frederic Weisbecker , linux-kernel@vger.kernel.org, Greg KH , Thomas Gleixner , Andrew Morton , John Kacur , Al Viro , Ingo Molnar References: <1273957196-13768-1-git-send-email-arnd@arndb.de> <201006192229.21971.arnd@arndb.de> <20100619225706.340eda52@lxorguk.ukuu.org.uk> In-Reply-To: <20100619225706.340eda52@lxorguk.ukuu.org.uk> MIME-Version: 1.0 Content-Type: Text/Plain; charset="iso-8859-1" Content-Transfer-Encoding: 7bit Message-Id: <201006202254.34530.arnd@arndb.de> X-Provags-ID: V01U2FsdGVkX18fpfRT31T8oLrVA0IRj8PL6D7EacEEsiNtwBM uF9KufIgXVtyXswZN2KpsEdXVEx8yjIg2eGKLgA+HZHJ9dTTfm njIX+leA78yqleeJG9nUw== Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Saturday 19 June 2010 23:57:06 Alan Cox wrote: > > Important question - does it need a getty or will a simple cat < /dev/foo > twice get garbled (or cat > if its garbling the other way) > > Which direction matters and whether a hangup is needed matters What I see is totally reproducible but does not make any sense to me. In my test setup I have a serial cable between /dev/ttyS0 (on-board 16550A) and /dev/ttyUSB0 on the same machine. When I start minicom on ttyS0 (or cat, for that matter), and start a getty on ttyUSB0 (or write into it any other way), everything is totally fine. I can observe the following problems when I start minicom on ttyUSB0: - writing to ttyS0 using cat alone gives garbled output - writing to ttyS0 using minicom always works - running a getty on ttyS0 lets me log in once - writing to ttyS0 using cat works fine while a working getty or minicom also has ttyS0 open - running the getty on ttyS0 a second time gives me the same garbled output as cat gives me The way that the output is garbled seems to be just missing characters, in a mostly reproducible way. Repeatedly writing the string abcdefghijklmnopqrstuvwxyz1234567890 into ttyS0 gives an output like 'akq7m3iy', where only every sixteenth character is shown, plus an extra character in the second position. Arnd