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From: Kumar Gala <galak@kernel.crashing.org>
To: Timur Tabi <timur@freescale.com>
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Subject: Re: removing get_immrbase()??
Date: Wed, 22 Apr 2009 16:54:07 -0500
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On Apr 22, 2009, at 4:46 PM, Timur Tabi wrote:

> Kumar Gala wrote:
>
>> The specific issue I'm talking about is the addition of new nodes  
>> that
>> might break old device trees.
>
> New nodes or new properties?  The CPM nodes are not new.  On some  
> device
> trees, the original versions did not have a compatible property for  
> the
> CPM nodes (e.g. commit 0b5cf10691eb2c95a9126bf25f5e084d83d5d743).
> Therefore, there are device trees out there that are missing some  
> property.
>
> Like I said earlier, if you can demonstrate that *all* of these device
> tree would be broken with the latest kernel anyway, then we don't need
> to worry about backwards compatibility.
>
> I'm tired of debugging customer issues where the kernel is updated but
> the firmware and device tree aren't.  IMHO, Kernel developers are
> generally too lax when it comes to firmware and device tree backwards
> compatibility, and I think that's wrong.

New nodes.  For example I've proposed a "local access window" node.   
Once I add it I plan on changing code to use it.  This will break an  
old device tree booting with the new kernel and I'm completely ok with  
that.

- k