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    SubjectRe: [PATCH, RAW] IRQ: Maintain irq number globally rather than passing to IRQ handlers
    Linus Torvalds wrote:
    > On Fri, 6 Oct 2006, Jeff Garzik wrote:
    >> Here is the raw, un-split-up first pass of the irq argument removal patch
    >> (500K):
    > So I'm not at all as sure about this as about the "regs" stuff.
    > The "regs" value has always been controversial. It's pretty much always
    > existed (due to the keyboard hander and the magic debugging keysequences),
    > and anybody who looks at 0.01 will quickly realize that the keyboard
    > driver was one of the very first drivers (I think it's even written in
    > assembly at that point: originally _all_ of what was to become Linux was
    > pure asm, the whole "oh, cool, I could write this part in C" came later).
    > But it's been pretty much a special case since day #1, purely for that
    > "press a key to see where the h*ck we hung" case.

    Chuckle :)

    > In contrast, the irq argument itself is really no different from the
    > cookie we pass in on registration - it's just passing it back to the
    > driver that requested the thing. So unlike "regs", there's not really
    > anything strange about it, and there's nothing really "wrong" with having
    > it there.

    It doesn't have the colorful history of pt_regs, but the 'irq' argument
    is dead weight. I'd say the wrongness stems from its utter uselessness.

    Out of ~1100 irq handlers, the irq parameter is used in ~50. The vast
    majority of those 50 uses are debug printks, or abused as a "did I call
    myself?" internal driver flag. The number of "real" uses is under 15,
    and those are all ancient ISA or platform drivers that pre-date my ~10
    year history with Linux.

    So, I don't see any convincing argument to keep it. And if we are going
    to kill it, given the pt_regs churn, this is probably the best
    opportunity we'll have in years.

    Another weak-but-still-present argument in favor of killing it is that
    this change would IMO future-proof irq handlers, against more exotic irq
    handling methods that may come down the pipe.


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