From mboxrd@z Thu Jan 1 00:00:00 1970 From: Stephen Hemminger Subject: Re: [RFC] net/hsr: Add support for IEC 62439-3 High-availability Seamless Redundancy Date: Tue, 3 Apr 2012 11:37:51 -0700 Message-ID: <20120403113751.21fd0b17@s6510.linuxnetplumber.net> References: <4F71BEAD.5080605@enea.com> Mime-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit Cc: "David S. Miller" , , Bruno Ferreira To: Arvid Brodin Return-path: Received: from mail.vyatta.com ([76.74.103.46]:55767 "EHLO mail.vyatta.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1754544Ab2DCSh5 (ORCPT ); Tue, 3 Apr 2012 14:37:57 -0400 In-Reply-To: <4F71BEAD.5080605@enea.com> Sender: netdev-owner@vger.kernel.org List-ID: On Tue, 27 Mar 2012 15:20:45 +0200 Arvid Brodin wrote: > +config NONSTANDARD_HSR > + bool "HSR: Use efficient tag (breaks HSR standard, read help!)" > + depends on HSR > + ---help--- > + The HSR standard specifies a 6-byte HSR tag to be inserted into the > + transmitted network frames. This breaks the 32-bit alignment that the > + Linux network stack relies on, and would cause kernel panics on > + certain architectures. To avoid this, the whole frame payload is > + memmoved 2 bytes on reception on these architectures - which is very > + inefficient! This option won't fly. Don't do it. If you need to copy/realign packets on some architecture the stack should be changed to handle it.