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    SubjectRe: [GIT PATCH] more Driver core patches for 2.6.19
    On Thu, 2006-12-14 at 09:14 +1100, Benjamin Herrenschmidt wrote:
    > the edge flow is easy. the level one is:
    > - IRQ happens
    > - kernel handler masks it and queue a msg for userland
    > - later on, userland gets the message, talks to the device,
    > (MMAP'ed mmio, acks the interrupt on the device itself) and
    > does an ioctl/syscall/write/whatever to tell kernel it's done
    > - kernel unmasks it.

    That's simply not true.

    - IRQ happens
    - kernel handler runs and masks the chip irq, which removes the IRQ
    - user space message get queued or waiting reader woken
    - kernel handler returns IRQ_HANDLED, which reenables the irq in the PIC
    - user space handles the device
    - user space reenables the device irq

    No need for an ioctl. Neither for edge nor for level irqs.


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