Date: Wed, 29 Sep 2010 12:07:27 -0400 From: Deepa Srinivasan <dsriniv@ncsu.edu> To: freebsd-drivers@freebsd.org Subject: Requesting an IRQ Message-ID: <AANLkTikS%2BtwoJTCm82wgo357Z8%2Bz8Kcp1vji0cmB=KiP@mail.gmail.com>
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I'm writing a "pseudo" device driver for FreeBSD 5.0 - i.e. there is no physical device backing it. But I need to be able to send an interrupt to it from an underlying hypervisor (KVM). FreeBSD runs as a guest OS. I have done the same in Linux - wrote a kernel module and used the "request_irq" function to allocate an unused interrupt number. When the underlying KVM injects an interrupt into the guest OS, the registered interrupt handler gets called as expected. However, in FreeBSD, I cannot find an equivalent function to "request_irq". Going with the available documentation and sample code, I tried modifying a PCI driver (this may be overkill for what I'm doing, but still...) and used the bus_alloc_resource() and bus_setup_intr() functions. In my OS configuration, this results in the "irq9" being allocated to my driver. But the same IRQ is also allocated to "acpi0". Now, when I inject an interrupt from the hypervisor, it immediately causes an "interrupt storm" and I see this message continuously printed: "interrupt storm detected on irq9; throttling interrupt source". This happens even without my driver being loaded. In the KVM hypervisor code, I set the interrupt to "1" and immediately to "0" and I know for sure that this code path is being executed. My question is: - Is it possible to write a pseudo device driver and use something like the "request_irq" in Linux to just be able to invoke a callback function in the driver? - Is it possible to specify the interrupt number that needs to be allocated to my device driver so I can ensure that it is not shared with anything else? Thanks for any help. - Deepa
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