[RFC PATCH 13/14] ARM: vexpress: Definition of vexpress dts specification

[Grant Likely]

On Fri, Aug 20, 2010 at 3:03 PM, M. Warner Losh <imp at bsdimp.com> wrote:
> In message: <AANLkTi=WiHd06=e4d_WdCe+HMfFhj-Q=xRS_4f-TzGUs at mail.gmail.com>
>            Grant Likely <grant.likely at secretlab.ca> writes:
> : Regardless though, the linux mapping doesn't actually have any bearing
> : on the device tree because the mapping from HW to linux irq number is
> : all internal to the kernel.  The kernel could choose to start the
> : mapping at 42 or somewhere else and it would all still work.
>
> Some (all?) PowerPC platforms start their interrupt numbering at 16,
> since interrupts 0-15 are reserved for old-school ISA interrupts from
> the Super I/O chip that may (or may not) be present on these systems.
> It's all handled inside the kernel, so is invisible to the
> device-tree, as Grant is saying.  Also, more OSes than Linux use
> device trees, so hard-coding Linux IRQ numbers would be displeasing
> from that point of view.

Yes, good point Warner.  In fact, that 16 offset has nothing to do
with the hardware, but rather to legacy drivers which have their irq
numbers hard coded in the 0-15 range.

g.