[PATCH 1/2] [ARM] Introduce 'struct machine_class' for SoC level abstraction

[Russell King - ARM Linux]

On Mon, Jun 21, 2010 at 04:23:22PM +0800, Eric Miao wrote:
> So that from derivative POV, it can be expressed as:
> 
> 	if (mdesc->class && mdesc->class->map_io)
> 		mdesc->class->map_io();
> 	if (mdesc->map_io())
> 		mdesc->map_io();
> 
> But this seems to make things a bit over complicated, so for such cases
> I'd prefer:
> 
> 1. have a separate machine_class for mainstone
> 2. or move the board specific map_io() separatedly

How about making the presence of mdesc->map_io override the class
version?

So if mainstone provides its own map_io() function, it is still
responsible (as is today) for calling the PXA specific map_io().
The same behaviour seems sensible to apply to the other class
functions as well - allow platforms to override the class
version, and leave the replacement platform function responsible
for calling the class if that's what it needs to do.