FreeBSD Device Drivers

Message Signaled Interrupts

Message Signaled Interrupts (MSI) and Extended Message Signaled Interrupts (MSI-X) are alternative ways to send interrupts. Traditionally, devices include an interrupt pin that they assert in order to generate an interrupt, but MSI- and MSI-X-enabled devices send some data, known as an MSI message or MSI-X message, to a particular memory address in order to generate an interrupt. MSI- and MSI-X-enabled devices can define multiple unique messages. Subsequently, drivers can define multiple unique interrupt handlers. In other words, MSI- and MSI-X-enabled devices can issue different interrupts, with each interrupt specifying a different condition or task. MSI- and MSI-X-enabled devices can define up to 32 and 2,048 unique ...