On Tue, 5 Jun 2012, Marek Vasut wrote:
> > > > Do the tests in the opposite order and add "unlikely":
> > > > if (unlikely(ehci->transceiver &&
> > > >
> > > > (pstatus & PORT_CSC)) {
> > > >
> > > > That way it will fail more quickly on systems where it doesn't apply or
> > > > for unaffected ports.
> > >
> > > Does this unlikely() have any effect on ARM/MIPS/PPC, where this chipidea
> > > IP is used ? Or is there some x86 device sporting this IP too?
> >
> > I don't know what unlikely() does on architectures other than x86.
>
> It should be optimized out to nothing on anything else but x86. On x86 it is a
> hint for the branch predictor. Or that's what I believe it is.
That's right. Then it should have no effect on ARM/MIPS/PPC.
> > And
> > I haven't heard of any x86 systems that would need to use this code.
> >
> > On the other hand, port-status changes don't occur very frequently. A
> > little time penalty one way or the other won't make much difference.
>
> I'm not opposed, just curious :)
No big deal either way. But the order of the tests should be switched,
because on most systems, ehci->transceiver will be NULL.
Alan Stern
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