Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1764814AbYBPDmG (ORCPT ); Fri, 15 Feb 2008 22:42:06 -0500 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1755585AbYBPDlt (ORCPT ); Fri, 15 Feb 2008 22:41:49 -0500 Received: from py-out-1112.google.com ([64.233.166.176]:13333 "EHLO py-out-1112.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753885AbYBPDlr (ORCPT ); Fri, 15 Feb 2008 22:41:47 -0500 Message-ID: Date: Fri, 15 Feb 2008 22:41:46 -0500 From: "Kyle Moffett" To: "Linux NetDev" , LKML , "Stephen Hemminger" Subject: [RFC] Best method to control a "transmit-only" mode on fiber NICs (specifically sky2) MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit Content-Disposition: inline Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1703 Lines: 35 Hi, The company I'm working for has an unusual fiber NIC configuration that we use for one of our network appliances. We connect only a single fiber from the TX port on one NIC to the RX port on another NIC, providing a physically-one-way path for enhanced security. Unfortunately this doesn't work with most NIC drivers, as even with auto-negotiation off they look for link probe pulses before they consider the link "up" and are willing to send packets. We have been able to use Myricom 10GigE NICs with a custom firmware image. More recently we have patched the sky2 driver to turn on the FIB_FORCE_LNK flag in the PHY control register; this seems to work on the Marvell-chipset boards we have here. What would be the preferred way to control this "force link" flag? Right now we are accessing it using ethtool; we have added an additional "duplex" mode: "DUPLEX_TXONLY", with a value of 2. When you specify a speed and turn off autonegotiation ("./patched-ethtool -s eth2 speed 1000 autoneg off duplex txonly"), it will turn on the specified bit in the PHY control register and the link will automatically come up. We also have one related bug-fix^Wdirty hack for sky2 to reset the PHY a second time during netif-up after enabling interrupts; otherwise the immediate "link up" interrupt gets lost. Once I get approval from the company I will patch the post itself for review. I look forward to your comments and suggestions Cheers, Kyle Moffett -- 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/