[PATCH 2/2] powerpc: add support for MPIC message register API

[Kushwaha Prabhakar-B32579]

> > Hi,
> >
> > I have no comments about coding and architecture. It looks fine.
> >
> > Only have a query about its use case..
> >    "Any application intended to use message interrupt requires to know
> reg_num because of struct mpic_msgr* mpic_msgr_get(unsigned int reg_num)
> API"
> >
> > It will be good to search available unit internally and provide its
> pointer. It will make application more flexible.
> >
> 
> The problem is that you fundamentally cannot implement an allocator for
> MSG registers if you're going to communicate with another kernel (how
> would both kernels' allocators be synchronized?). So the message register
> allocation must be decided at design time, not run time.
> 

I agree with you..  It is true while communicating with another kernel.
But message interrupts can be used by different independent drivers within same kernel. For eg. PCIe and Ethernet driver. 
As per current design both drivers needs to be in sync before requesting any message unit for avoiding any conflict. As these drivers are completely independent. It is very difficult. 

Can it be possible to provide new API to take care it.

--Prabhakar