Did PCI/IRQ allocation change significantly after 4.2 kernel?

[Rob Groner]

And, we have a winner!

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rtd at kernel-dev:~/git/kernels/linux$ git bisect good
991de2e59090e55c65a7f59a049142e3c480f7bd is the first bad commit
commit 991de2e59090e55c65a7f59a049142e3c480f7bd
Author: Jiang Liu <jiang.liu at linux.intel.com>
Date:   Wed Jun 10 16:54:59 2015 +0800

    PCI, x86: Implement pcibios_alloc_irq() and pcibios_free_irq()
    
    To support IOAPIC hotplug, we need to allocate PCI IRQ resources on
demand
    and free them when not used anymore.
    
    Implement pcibios_alloc_irq() and pcibios_free_irq() to dynamically
    allocate and free PCI IRQs.
    
    Remove mp_should_keep_irq(), which is no longer used.
    
    [bhelgaas: changelog]
    Signed-off-by: Jiang Liu <jiang.liu at linux.intel.com>
    Signed-off-by: Bjorn Helgaas <bhelgaas at google.com>
    Acked-by: Thomas Gleixner <tglx at linutronix.de>

:040000 040000 765e2d5232d53247ec260b34b51589c3bccb36ae
f680234a27685e94b1a35ae2a7218f8eafa9071a M	arch
:040000 040000 d55a682bcde72682e883365e88ad1df6186fd54d
f82c470a04a6845fcf5e0aa934512c75628f798d M	drivers
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I'll sort out what all of that means tomorrow...

Rob