vt8500: multiplatform for 3.8

I just took a cursory look over the work required for enabling multiplatform support for v3.8 for arch-vt8500.

There are 2 files I don't know what to do with in
arch-vt8500/include/mach:

1) entry-macro.S
Contains some low-level irq macro's.

2) irqs.h
Only contains '#define NR_IRQS 128' so I thought it would be easy enough to get rid of, but it looks like I need to enable SPARSE_IRQ to drop it, which will require some coding - what exactly is SPARSE_IRQ and what's required to make it work?

Regards

Tony P

The solution is to enable CONFIG_MULTI_IRQ_HANDLER (implied in CONFIG_MULTIPLATFORM), and implement the same code in C, and then set the .handle_irq callback in the your machine descriptor to this function.

SPARSE_IRQ (in combination with IRQDOMAIN) removes the direct mapping between hardware IRQ numbers and Linux IRQ numbers. You already have IRQ domain support in the irq driver. If all IRQ numbers are parsed from the device tree, you can convert this from legacy to linear domain to cut the last ties (the local irq_cnt variable) and just set SPARSE_IRQ without reserving any legacy interrupts. Some platforms put an nr_irqs variable into the machine descriptor as an intermediate step, but I think you don't even need that.

Arnd