Re: [PATCH v8 24/25] powerpc: Adopt nvram module for PPC64

[Finn Thain]

On Tue, 8 Jan 2019, Michael Ellerman wrote:

> > The reason why that doesn't work boils down to introspection. (This 
> > was mentioned elsewhere in this email thread.) For example, we 
> > presently have code like this,
> >
> > ssize_t nvram_get_size(void)
> > {
> >        if (ppc_md.nvram_size)
> >                return ppc_md.nvram_size();
> >        return -1;
> > }
> > EXPORT_SYMBOL(nvram_get_size);
> >
> > This construction means we get to decide at run-time which of the NVRAM 
> > functions should be used. (Whereas your example makes a build-time decision.)
> 
> Right, but we only need to make a runtime decision on powerpc (right?).

It's needed in many places outside of powerpc. Otherwise the caller can't 
determine at run-time which ops are implemented.

Hence you have to duplicate the caller for each supported configuration 
that you build.

Already, this precludes a shared misc device implementation and belies the 
"generic" in drivers/char/generic_nvram.c.

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