Subject: Re: [PATCH] powerpc: consolidate mpc83xx platform files

From: Scott Wood <[email-masked]>
Date: Tue, 12 Dec 2006 16:41:19 -0600

Kumar Gala wrote:
> On Dec 12, 2006, at 3:30 PM, Scott Wood wrote:
>> They *may* not want to (and they certainly shouldn't be forced to),  but
>> some may not want to define a new ppc_md (or modify a probe function)
>> for every new board if all of the differences are encapsulated in the
>> device tree.  I thought one of the main goals of having a device  tree is
>> that if it's done right, the kernel need not know about every single
>> model of board, just the different components that a device tree can
>> specify.
> 
> That's true, and if that's the case you'd just set your "model" to  
> match an existing supported ppc_md.

Having an 831x explicitly claim to be an 834x is just a tad icky...

>> If a board has truly board-specific logic that needs custom code in  the
>> kernel itself (rather than the bootloader), then it can go in as a
>> driver with a device tree node (this should be done with the BCSR  stuff
>> where needed).
> 
> This is not always the case, there are times when you have board  
> specific modifications you make in the early kernel code.

Sure -- I'm not proposing doing away with board-specific machine 
descriptions entirely, just reducing the circumstances where they're 
required.

> True, but I dont see what the desire is to create a 'generic' 83xx  
> support.  Who gets to define what is considered 'generic'?  

"Generic" is any board that has needs that aren't expressed in the 
device tree.

> I'm all for refactoring code so my board code  
> is simpler, but at the end of the day I know there are people that  are 
> going to need board specific code for their environments.

And an 83xx-generic machine description does not stop them from doing 
so.  "Generic" does not mean "universal".  It means "there's nothing 
special about this board".  If you need board-specific code in the 
kernel, then don't label it generic.

-Scott