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    SubjectRe: User mode drivers: part 1, interrupt handling (patch for 2.6.11)
    >>>>> "Jon" == Jon Smirl <jonsmirl@gmail.com> writes:

    Jon> On Fri, 11 Mar 2005 14:36:10 +1100, Peter Chubb
    Jon> <peterc@gelato.unsw.edu.au> wrote:
    >> As many of you will be aware, we've been working on infrastructure
    >> for user-mode PCI and other drivers. The first step is to be able
    >> to handle interrupts from user space. Subsequent patches add
    >> infrastructure for setting up DMA for PCI devices.

    Jon> I've tried implementing this before and could not get around the
    Jon> interrupt problem. Most interrupts on the x86 architecture are
    Jon> shared. Disabling the IRQ at the PIC blocks all of the shared

    Fortunately, most interrupts on IA64, ARM, etc., are unshared. And
    with PCI-Express, the problem will go away. Even on X86, things
    aren't all bad: one can usually find a PCI slot which doesn't share
    interrupts with anything you care about.

    The scenario I'm thinking about with these patches are things like
    low-latency user-level networking between nodes in a cluster, where
    for good performance even with a kernel driver you don't want to share
    your interrupt line with anything else.

    --
    Dr Peter Chubb http://www.gelato.unsw.edu.au peterc AT gelato.unsw.edu.au
    The technical we do immediately, the political takes *forever*
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