Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1757918AbXENSK2 (ORCPT ); Mon, 14 May 2007 14:10:28 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1756183AbXENSKW (ORCPT ); Mon, 14 May 2007 14:10:22 -0400 Received: from caramon.arm.linux.org.uk ([217.147.92.249]:2264 "EHLO caramon.arm.linux.org.uk" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1755707AbXENSKV (ORCPT ); Mon, 14 May 2007 14:10:21 -0400 Date: Mon, 14 May 2007 19:10:08 +0100 From: Russell King To: Yinghai Lu Cc: Andrew Morton , Andi Kleen , bjorn.helgaas@hp.com, Randy Dunlap , Linux Kernel Mailing List Subject: Re: [PATCH] serial: set RTS and DTR if flow is 'r' --- resend Message-ID: <20070514181007.GA29682@flint.arm.linux.org.uk> Mail-Followup-To: Yinghai Lu , Andrew Morton , Andi Kleen , bjorn.helgaas@hp.com, Randy Dunlap , Linux Kernel Mailing List References: <86802c440705122233y327756e7te534199f46b2059d@mail.gmail.com> <46489BC2.6040403@sun.com> <4648A310.1050908@sun.com> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <4648A310.1050908@sun.com> User-Agent: Mutt/1.4.2.1i Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1553 Lines: 35 On Mon, May 14, 2007 at 10:57:36AM -0700, Yinghai Lu wrote: > [PATCH] serial: set RTS and DTR if flow is 'r' > > if the serial console flow is set to 'r', We need to set RTS and DTR. > Some UARTs on other side need these bit set, otherwise will not send > char to or > receive char from the host that kernel is runing esp for kernel boot stage. Patch is still broken. Patch is completely wrong as well - we do _not_ want to set the RTS and DTR bits here, and is in fact undoing a fix I put in over the 2.4 drivers. If CRTSCTS is enabled via userspace, and the port is not being used as a console, we do not want to raise RTS _until_ we are ready to receive characters. Your patch breaks this. Moreover, I question the reasoning. RTS is normally raised to allow the remote end to send characters. Since the kernel console is output _only_, until userspace opens it, there's little point in raising RTS. RTS will be raised when userspace opens it. There may be some sense, however, in allowing DTR to be permanently raised for serial consoles. However, I would err on caution since DTR is used to reliably instruct modems to drop the line, so making such a change would be undesirable for those folk. -- Russell King Linux kernel 2.6 ARM Linux - http://www.arm.linux.org.uk/ maintainer of: - 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/