Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id ; Mon, 30 Jul 2001 19:34:20 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id ; Mon, 30 Jul 2001 19:34:01 -0400 Received: from h24-64-71-161.cg.shawcable.net ([24.64.71.161]:10741 "EHLO webber.adilger.int") by vger.kernel.org with ESMTP id ; Mon, 30 Jul 2001 19:33:42 -0400 From: Andreas Dilger Message-Id: <200107302332.f6UNWbxg001791@webber.adilger.int> Subject: Re: Support for serial console on legacy free machines In-Reply-To: <3B65E711.A3828E15@fc.hp.com> "from Khalid Aziz at Jul 30, 2001 05:00:33 pm" To: Khalid Aziz Date: Mon, 30 Jul 2001 17:32:37 -0600 (MDT) CC: Andreas Dilger , Linux kernel development list X-Mailer: ELM [version 2.4ME+ PL87 (25)] MIME-Version: 1.0 Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org Original-Recipient: rfc822;linux-kernel-outgoing Khalid Aziz writes: > Andreas Dilger wrote: > > What bothers me is that new systems don't have a serial port, and no ISA > > slots, so there is no hope of getting a "serial console" support without > > ACPI (which is rather heavyweight AFAIK). USB is far too complex to use > > for early-boot debugging, so what else is left? > > I am puzzled. How would you get "serial console" support even with ACPI > unless there IS a serial port on the system????? All ACPI can do is tell > you where the serial port is. OK, maybe I'm misunderstanding here, but even if I put in a PCI serial card in such a machine, can I get serial console support without ACPI? Not that it matters in my case, because there are no PCI slots on the motherboard either. > > There was some talk about using a low level IP console over ethernet, > > but I would imagine this is more complex than the same thing on a > > parallel-port. I could be wrong. Of course, an IP console has the > > advantage of being useful over a longer distance than a parallel cable, > > but may have the disadvantage of poor security. > > IP console qould require a significant amount of network protocol stack > to be up and running. That would make console available pretty late in > bootup sequence. Yes, this is another good reason why an IP console is less desirable. AFAIK, some systems have such IP console support in BIOS (it may not even be "IP" but raw ethernet). > Even if console were to be used to print just errors and information > messages, it should still be pretty simple to ensure those messages > do get printed out. A serial port meets those requirements. And I think "legacy" parallel ports also meet this simplicity requirement as well, except for the fact that until now it was much more common to also have a serial port, so nobody has done the work to have bidirectional parallel port support. Sadly, I have _no_ idea even where to begin on it, nor the time. I was hoping someone would chime in and say "I did that already". I guess the other need would be to allow programs like minicom, kgdb, etc to open /dev/lp0 like a serial port on the client side, so we don't need to re-write all of the user-space tools as well. Cheers, Andreas -- Andreas Dilger \ "If a man ate a pound of pasta and a pound of antipasto, \ would they cancel out, leaving him still hungry?" http://www-mddsp.enel.ucalgary.ca/People/adilger/ -- Dogbert - To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/