From mboxrd@z Thu Jan 1 00:00:00 1970 From: Geert Uytterhoeven Subject: Re: post 3.14 serial regression Date: Wed, 9 Apr 2014 22:59:27 +0200 Message-ID: References: <5343416F.8010201@sr71.net> <20140408122726.227f3da8@alan.etchedpixels.co.uk> <5344642A.2020703@sr71.net> <53446C57.5000504@intel.com> <20140409003648.GB32273@kroah.com> <5345A7B3.7020005@sr71.net> Mime-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Return-path: Received: from mail-pb0-f41.google.com ([209.85.160.41]:54818 "EHLO mail-pb0-f41.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S932847AbaDIU72 (ORCPT ); Wed, 9 Apr 2014 16:59:28 -0400 In-Reply-To: <5345A7B3.7020005@sr71.net> Sender: linux-serial-owner@vger.kernel.org List-Id: linux-serial@vger.kernel.org To: Dave Hansen Cc: Greg Kroah-Hartman , Dave Hansen , One Thousand Gnomes , Geert Uytterhoeven , LKML , linux-serial@vger.kernel.org, Jiri Slaby Hi Dave, On Wed, Apr 9, 2014 at 10:04 PM, Dave Hansen wrote: > On 04/09/2014 12:41 PM, Geert Uytterhoeven wrote: >> Dave: If I understand it correctly, you use console=ttyS2, while the kernel >> suddenly changed the order of the serial devices, so your port is no >> longer ttyS2, but ttyS4. Hence the serial port is not found, and >> uart_remove_one_port() is called on it, taking away your /dev/console for >> userspace? > > Right. Does it work with console=ttyS4? >>>>From the backtrace, it's the call below to uart_remove_one_port() >> that removes the port? >> >> /** >> * serial8250_register_8250_port - register a serial port >> * @up: serial port template >> * >> * Configure the serial port specified by the request. If the >> * port exists and is in use, it is hung up and unregistered >> * first. >> * >> * The port is then probed and if necessary the IRQ is autodetected >> * If this fails an error is returned. >> * >> * On success the port is ready to use and the line number is returned. >> */ >> int serial8250_register_8250_port(struct uart_8250_port *up) >> { >> ... >> >> if (uart && uart->port.type != PORT_8250_CIR) { >> if (uart->port.dev) >> uart_remove_one_port(&serial8250_reg, &uart->port); >> >> where was it added before? > > Remember, serial8250_find_match_or_unused() will also reuse *EXISTING* > uart_ports if the port is of 'unknown' type. > > I believe that port got added during the addition of the > serial8250_isa_devs, and now we're trying to reuse it since it is an > unknown port type. So it gets added, removed, and added again. I also noticed that unbinding and rebinding the driver doesn't re-attach it as a serial console. Gr{oetje,eeting}s, Geert -- Geert Uytterhoeven -- There's lots of Linux beyond ia32 -- geert@linux-m68k.org In personal conversations with technical people, I call myself a hacker. But when I'm talking to journalists I just say "programmer" or something like that. -- Linus Torvalds