[U-Boot] [PATCH] Honor /memory/reg node in DTB files

[Wolfgang Denk]

Dear Deepak Saxena,

In message <4D026BB2.6020609 at mentor.com> you wrote:
> On 12/08/2010 02:34 PM, Wolfgang Denk wrote:
> 
> > 
> > I guess we can argue that the normal situation is that U-Boot will
> > know how to update the DT such as needed to boot the OS. So what we
> > are dealing with is a small percentage of cases where we need special
> > behaviour, and where it may be acceptable if the solution is only
> > semi-perfect ;-)
> > 
> > My current thinking is to introduce something like
> > 
> > 	dt_skip=memory,mac-address
> > 
> > including eventually "dt_skip=ALL".  This should cover most of the
> > current use cases.
> > 
> > If someone gets fancy he can add wildcard support.
> > 
> > And if we need even more flexibility, we can add some "dt_include"
> > with higher priority, so one could do for example
> > 
> > 	dt_skip=ALL
> > 	dt_include=memory
> 
> I imagine this being rather ugly to implement and to keep the code clean
> and maintained. Who parses these variables? Does each and every piece of
> code in U-Boot that now touches a piece of the DT need to check for this
> variable? I could see something like this working
> if there was a central DT handler that read nodes and then called
> platform-specific over-ride function, i.e.:
> 
> 	for_each_node_in_dt() {
> 		if (dt_include(node->type))
> 			platform_of_dt_node_process(node, boot_stage);
> 	}
> 
> 	where boot_stage tells us whether we are at early init, about to
>         boot an OS image, or in some other step in the process.
> 
> This would provide a consistent method of handling that variable.
> Without something like this, I think and environment variable is just
> going to create confusion for users and developers.

You just described what the implementation should look like.

Thanks.

Wolfgang Denk

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