FreeBSD Device Drivers

Implementing MSI

Unlike with previous topics, I’m going to take a holistic approach here. Namely, I’m going to show an example first, and then I’ll describe the MSI family of functions.

The following function, named ciss_setup_msix and defined in /sys/dev/ciss/ciss.c, sets up MSI for the ciss(4) driver.

Note

This function was chosen solely because it’s simple. The fact that it’s from ciss(4) is irrelevant.

static int
ciss_setup_msix(struct ciss_softc *sc)
{
        int i, count, error;

        i = ciss_lookup(sc->ciss_dev);
      if (ciss_vendor_data[i].flags & CISS_BOARD_NOMSI)
                return (EINVAL);

        count = pci_msix_count(sc->ciss_dev); if (count < CISS_MSI_COUNT) { count = ...