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SubjectRe: Handling interrupts from userspace

On Wed, 28 Jul 1999, Mark Hahn wrote:

> > If this is not possible ... is there any _generic_ driver to which I could
> > "attach" a userspace application in order for this app to know when an
> > interrupt has happened ?!?!
>
> yes, a generic driver could exist.
^^^^^
From your answer, I assume it does not exist _yet_. Is that correct ??

What I'm looking for is a driver _already in the kernel_ that would allow
me to tell it "watch this interrupt line and tell me when it is asserted,
and I will then handle the interrupt request".

Or (if possible) register the interrupt _from userspace_ and handle it
directly. Is it possible ?!?!

> normally, a user-level process
> would just do a blocking read or ioctl, and the driver would sleep
> the process until an interrupt comes in.

The problem with that is that you're assuming there is already a driver
for this specific device. I'm trying to write a HW test application that
does _not_ depend on a specific driver to work, an application that can
access the specific HW directly and test it. I already know how to access
MMIO, the PCI bus and such, but I don't know how to handle interrupts from
userspace.

Suggstions ?!?!

> there are some issues with whether/how int's get ack'ed, masked, etc.
> but for a specific piece of hardware, it cold probably be done fine.

It would be nice, in this case, to have a generic driver in the kernel to
which you could say:
- Register this interrupt for me;
- When this interrupt is called, let me know and I'll handle it and clear
the interrupt request;
- (Optional)I'll let you know when I'm done handling it;

This would be great for HW debugging and diagnostics testing (which is
what I'm interested in).

Regards,
Ivan


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