Updating the define_machine() structure at runtime?

[Benjamin Herrenschmidt]

On Mon, 2011-05-16 at 11:21 -0500, Timur Tabi wrote:
> I would like to get some opinions on the following.
> 
> I'm working on extending our existing board definition files to support our
> ePAPR reference hypervisor.  Because our hypervisor provides a virtual PIC, we
> need to have different functions for define_machine() structure that related to
> the PIC, but most everything else can stay the same.

 .../...

> static int __init p4080_ds_probe(void)
> {
> 	...
> #ifdef CONFIG_FSL_HYPERVISOR
> 	if (of_flat_dt_is_compatible(root, "fsl,P4080DS-hv")) {
> 		mach_p4080_ds.get_irq = ehv_pic_get_irq;
> 		...
> 		return 1;
> 	} else
> 		return 0;
> #endif	

One approach i've been taking more often nowadays is to have the PIC
code setup the ppc_md hooks itself.

You don't need to do it in probe(), just in setup_arch or init_IRQ,
wherever you do your PIC discovery, have it set it up.

For example, xics sets get_irq itself, which is necessary because the
xics code itself can have multiple variants.

We could probably make mpic.c do the same when MPIC_PRIMARY is set (or
keep that a wrapper for now).
 
Cheers,
Ben.