Merge tag 'irqdomain-for-linus' of git://git.secretlab.ca/git/linux-2.6

that each one gets assigned non-overlapping allocations of Linux

IRQ numbers.

The number of interrupt controllers registered as unique irqchips

show a rising tendency: for example subdrivers of different kinds

such as GPIO controllers avoid reimplementing identical callback

mechanisms as the IRQ core system by modelling their interrupt

handlers as irqchips, i.e. in effect cascading interrupt controllers.

Here the interrupt number loose all kind of correspondence to

hardware interrupt numbers: whereas in the past, IRQ numbers could

be chosen so they matched the hardware IRQ line into the root

interrupt controller (i.e. the component actually fireing the

interrupt line to the CPU) nowadays this number is just a number.

For this reason we need a mechanism to separate controller-local

interrupt numbers, called hardware irq's, from Linux IRQ numbers.

The irq_alloc_desc*() and irq_free_desc*() APIs provide allocation of

irq numbers, but they don't provide any support for reverse mapping of

the controller-local IRQ (hwirq) number into the Linux IRQ number

When an interrupt is received, irq_find_mapping() function should

be used to find the Linux IRQ number from the hwirq number.

The irq_create_mapping() function must be called *atleast once*

before any call to irq_find_mapping(), lest the descriptor will not

be allocated.

If the driver has the Linux IRQ number or the irq_data pointer, and

needs to know the associated hwirq number (such as in the irq_chip

callbacks) then it can be directly obtained from irq_data->hwirq.

Most users of legacy mappings should use irq_domain_add_simple() which

will use a legacy domain only if an IRQ range is supplied by the

system and will otherwise use a linear domain mapping.

system and will otherwise use a linear domain mapping. The semantics

of this call are such that if an IRQ range is specified then

descriptors will be allocated on-the-fly for it, and if no range is

specified it will fall through to irq_domain_add_linear() which meand

*no* irq descriptors will be allocated.

A typical use case for simple domains is where an irqchip provider

is supporting both dynamic and static IRQ assignments.

In order to avoid ending up in a situation where a linear domain is

used and no descriptor gets allocated it is very important to make sure

that the driver using the simple domain call irq_create_mapping()

before any irq_find_mapping() since the latter will actually work

for the static IRQ assignment case.

			irq_base = irq_alloc_descs(first_irq, first_irq, size,

						   of_node_to_nid(of_node));

			if (irq_base < 0) {

				WARN(1, "Cannot allocate irq_descs @ IRQ%d, assuming pre-allocated\n",

				pr_info("Cannot allocate irq_descs @ IRQ%d, assuming pre-allocated\n",

					first_irq);

				irq_base = first_irq;

			}