On Wed, Nov 07, 2007 at 01:09:40PM +0000, Alan Cox wrote:
However, platform_get_irq() will happily return IRQ#0, and it's a valid
vector on plenty of machines. NO_IRQ is also < 0 on at least FR-V, ARM,
blackin, PA-RISC, some PowerPC, and even IDE.
We do have some devices that are physically on IRQ#0 that otherwise work
fine, they aren't ATA devices mind you, but to claim that IRQ#0 isn't a
valid vector is not in line with what hardware actually does, whether
it's a good idea or not. In our case the IRQ vector maps to an exception
offset, which we bump down to zero. We could force an off-by-1 there so
that the math that indexes IRQ#0 is bumped up one, but that entails
fixing up every one of our IRQ numbers for no obvious gain.
I don't really see any value in purposely crippling the range of
allowable vectors for these machines. Though I don't mind switching to a
NO_IRQ comparison instead of the < 0 case, so both can be handled.