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SubjectRe: [GIT PATCH] more Driver core patches for 2.6.19


On Wed, 13 Dec 2006, Jan Engelhardt wrote:
>
> For the sharing case, some sort of softirq should be created. That is, when a
> hard interrupt is generated and the irq handler is executed, set a flag that at
> some other point in time, the irq is delivered to userspace. Like you do with
> signals in userspace:

NO.

The whole point is, YOU CANNOT DO THIS.

You need to shut the device up. Otherwise it keeps screaming.

Please, people, don't confuse the issue any further. A hardware driver

ABSOLUTELY POSITIVELY HAS TO

have an in-kernel irq handler that knows how to turn the irq off.

End of story. No ifs, buts, maybes about it.

You cannot have a generic kernel driver that doesn't know about the
low-level hardware (not with current hardware - you could make the "shut
the f*ck up" a generic thing if you designed hardware properly, but that
simply does not exist in general right now).

In short: a user-space device driver has exactly TWO choices:

- don't use interrupts at all, just polling

- have an in-kernel irq handler that at a minimum knows how to test
whether the irq came from that device and knows how to shut it up.

This means NOT A GENERIC DRIVER. That simply isn't an option on the
table, no matter how much people would like it to be.

Linus
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