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    SubjectRe: [PATCH] PCI: Add pci shutdown ability
    On Tue, 26 Apr 2005, Grant Grundler wrote:

    > > I looked into the possibility of having the PCI core disable interrupt
    > > generation and DMA on each new device as it is discovered. Unfortunately
    > > there is no dependable, universal way to do this for IRQs.
    >
    > Sure there is. Every IRQ line goes to an IRQ controller.
    > Arch specific code deals with programming the controller and can
    > mask all interrupts (or not). Historically, they've been left unmasked
    > for ISA IRQ discovery and debugging misrouted IRQ lines.

    This doesn't help. Consider what happens when two devices share an IRQ
    line. Suppose device B is generating interrupt requests when the driver
    for device A is probed. The driver registers its handler, which causes
    the IRQ line to be unmasked. Then a multitude of IRQs arrive from B, none
    of which can be handled by A's driver. So the kernel shuts the IRQ line
    down permanently...

    Alan Stern

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