Chuck Tuffli is working on an implementation of MSI for DragonFly. MSI is a way for device drivers to talk, similar to but better than the old IRQ method. As Chuck kindly explained it to me, MSI and MSI-X are necessary for PCI-Express support.
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One minor clarification. PCI-Express devices must support MSI or MSI-X, but that doesn’t mean an OS has to implement MSI(-X) to support PCIe devices. Many PCIe devices also emulate the legacy interrupt mode and thus can work with drivers and OS that know nothing about PCIe or MSI(-X).
Hi Chuck, how does a device driver request and use MSI? Can you show me a sample code (if_em.c?). Thanks.