Subject: Re: [RFC] net/hsr: Add support for IEC 62439-3 High-availability Seamless Redundancy

From: Stephen Hemminger <[email-masked]>
Date: Tue, 3 Apr 2012 11:37:51 -0700

On Tue, 27 Mar 2012 15:20:45 +0200
Arvid Brodin <[email-masked]> 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.