On Thu, 24 Apr 2008, Jeff Garzik wrote:However, it does not follow that an int is what _must_ be passed around. We
already have design patterns like
cookie_pointer = ioremap(raw bus resource)
Not that I am the one pushing for that, just noting.
I do agree that we could use something more type-safe.
So a "pointer" to a structure that doesn't actually exist would be fine and would give us some C type checking.
But then you'd have to have some way to "printk" the information, which is a very common requirement (and the printk still needs to be a number, because you want to match up 'dmesg' output with the '/proc/interrupts' file etc).
That, in turn, would effectively force a whole new function, and then you'd have things like
printk(.. irq %d .., irq_number(irqcookie) ..)
which while not ugly isn't really all that clean either. And I guarantee that people would misuse that "irq_number(cookie)" exactly in the same ways they'd misuse "irq" (ie not very much).
Quite frankly, I'd much prefer a
typedef int __bitwise irq_t;
and then we can use sparse to do this testing, without breaking any existing use at all (because it will still be an "int" to gcc, but sparse will make "irq_t" a type of its own and make sure that people pass it around as such and not do arithmetic ops on it etc).
EVERYTHING else would be architecture-specific. And that is exactly what weNot true -- you have metadata/OOB data like MSI messages, where you are passed
do not want. EVER.
a value from the PCI hardware in the PCI message, not just an "interrupt
asserted" condition. Or s/value/values/ if you enable PCI MSI's multiple
message support.
The point is, MSI *is* architecture-specific. In fact, it's even motherboard-specific, in that you are going to have (for the forseeable future) drivers that have to work with or witgout MSI even on the same architecture.