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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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