From mboxrd@z Thu Jan 1 00:00:00 1970 From: Arnd Bergmann Subject: Re: [RFC PATCH 1/2] OMAP2+: add cpu id register to MAC address helper Date: Fri, 25 Mar 2011 15:50:25 +0100 Message-ID: <201103251550.26117.arnd@arndb.de> References: <20110324211451.14936.39750.stgit@otae.warmcat.com> <201103251424.47141.arnd@arndb.de> <4D8C99CC.5020103@linaro.org> Mime-Version: 1.0 Content-Type: Text/Plain; charset="utf-8" Content-Transfer-Encoding: 7bit Return-path: Received: from moutng.kundenserver.de ([212.227.126.171]:51506 "EHLO moutng.kundenserver.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753701Ab1CYOuh (ORCPT ); Fri, 25 Mar 2011 10:50:37 -0400 In-Reply-To: <4D8C99CC.5020103@linaro.org> Sender: linux-omap-owner@vger.kernel.org List-Id: linux-omap@vger.kernel.org To: andy.green@linaro.org Cc: linux-arm-kernel@lists.infradead.org, linux-omap@vger.kernel.org, patches@linaro.org, nicolas.pitre@linaro.org, x0132446@ti.com, s-jan@ti.com, tony@atomide.com On Friday 25 March 2011, Andy Green wrote: > I see. It would work OK then. They probably wouldn't want to blow > their $1750 just on Panda though, so maybe they set 4 bits or whatever > and let 20 be computed. Well, if the algorithm is defined well, it could be used for any device based on OMAP. The marketing department could turn this into a win by declaring "does not require external EEPROM for ethernet mac address" ;-) > However, the only practical advantage is that it would show up as a TI > MAC in an OUI database. The "locally administered" address as used at > the moment is otherwise legal in every respect AFAIK. It should work almost always, except in very special corner cases: * If you have a netboot setup, you want the boot loader to use the same mac address for requesting the kernel image that you use later, otherwise the switch might consider it a MAC spoofing attach and disable the port. The obvious workaround is to put your code into the boot loader as well. * Some environments might be configured to disallow locally administered MAC addresses for "security" reasons. A bit bogus, but not unheard of. * Some places try to keep a database of all used machines and their MAC addresses to monitor who connects to the network. This requires the address to be stable. It also prevents the use of virtualization, so it's becoming less common. Arnd From mboxrd@z Thu Jan 1 00:00:00 1970 From: arnd@arndb.de (Arnd Bergmann) Date: Fri, 25 Mar 2011 15:50:25 +0100 Subject: [RFC PATCH 1/2] OMAP2+: add cpu id register to MAC address helper In-Reply-To: <4D8C99CC.5020103@linaro.org> References: <20110324211451.14936.39750.stgit@otae.warmcat.com> <201103251424.47141.arnd@arndb.de> <4D8C99CC.5020103@linaro.org> Message-ID: <201103251550.26117.arnd@arndb.de> To: linux-arm-kernel@lists.infradead.org List-Id: linux-arm-kernel.lists.infradead.org On Friday 25 March 2011, Andy Green wrote: > I see. It would work OK then. They probably wouldn't want to blow > their $1750 just on Panda though, so maybe they set 4 bits or whatever > and let 20 be computed. Well, if the algorithm is defined well, it could be used for any device based on OMAP. The marketing department could turn this into a win by declaring "does not require external EEPROM for ethernet mac address" ;-) > However, the only practical advantage is that it would show up as a TI > MAC in an OUI database. The "locally administered" address as used at > the moment is otherwise legal in every respect AFAIK. It should work almost always, except in very special corner cases: * If you have a netboot setup, you want the boot loader to use the same mac address for requesting the kernel image that you use later, otherwise the switch might consider it a MAC spoofing attach and disable the port. The obvious workaround is to put your code into the boot loader as well. * Some environments might be configured to disallow locally administered MAC addresses for "security" reasons. A bit bogus, but not unheard of. * Some places try to keep a database of all used machines and their MAC addresses to monitor who connects to the network. This requires the address to be stable. It also prevents the use of virtualization, so it's becoming less common. Arnd