ENUM VIRTIO_PCIDEV_OPS(9)

🌸 enum virtio_pcidev_ops(9) — bestie's guide to the virtual PCI device ops 💅

Okay so this is the <pink>enum virtio_pcidev_ops</pink> page from the Kernel API Manual, and honestly? It's giving "the entire vocabulary a virtual PCI device can speak." Every message type it can send or receive lives here. Let's get into it. ✨

✨ SYNOPSIS ✨

enum virtio_pcidev_ops {
    VIRTIO_PCIDEV_OP_RESERVED ,
    VIRTIO_PCIDEV_OP_CFG_READ ,
    VIRTIO_PCIDEV_OP_CFG_WRITE ,
    VIRTIO_PCIDEV_OP_MMIO_READ ,
    VIRTIO_PCIDEV_OP_MMIO_WRITE ,
    VIRTIO_PCIDEV_OP_MMIO_MEMSET ,
    VIRTIO_PCIDEV_OP_INT ,
    VIRTIO_PCIDEV_OP_MSI ,
    VIRTIO_PCIDEV_OP_PME

};

🎀 Constants — the whole squad 🎀

So these are all the possible ops, and each one is a different vibe of message. Here we go, no cap:

• VIRTIO_PCIDEV_OP_RESERVED — literally just sitting there to catch errors. It's the designated driver of this enum. 🙈
• VIRTIO_PCIDEV_OP_CFG_READ — read config space. The size is 1, 2, 4 or 8, and the data field should be filled in by the device, in little endian.
• VIRTIO_PCIDEV_OP_CFG_WRITE — write config space. Same size situation: 1, 2, 4 or 8. The data field contains the data to write, in little endian.
• VIRTIO_PCIDEV_OP_MMIO_READ — read BAR mem/pio. size can be variable here (not just the config-space sizes, watch out 👀). The data field should be filled in by the device, in little endian.
• VIRTIO_PCIDEV_OP_MMIO_WRITE — write BAR mem/pio. size can be variable. The data field contains the data to write, in little endian.
• VIRTIO_PCIDEV_OP_MMIO_MEMSET — memset MMIO. size is variable, BUT the data field only has one byte — unlike VIRTIO_PCIDEV_OP_MMIO_WRITE. Don't mix them up bestie, they are NOT the same. 😭
• VIRTIO_PCIDEV_OP_INT — legacy INTx# pin interrupt. The addr field is 1-4 for the number. Old-school but iconic.
• VIRTIO_PCIDEV_OP_MSI — MSI(-X) interrupt. This message basically transports the 16- or 32-bit write that would otherwise be done into memory — analogous to the write messages (VIRTIO_PCIDEV_OP_MMIO_WRITE) above. iykyk 🔥
• VIRTIO_PCIDEV_OP_PME — a dummy message whose content is ignored (and should be all zeroes) to signal the PME# pin. It's literally just there to say "hey, PME# happened" and nothing else. 🫶

🌈 SEE ALSO 🌈

• Kernel file ./include/uapi/linux/virtio_pcidev.h
• struct virtio_pcidev_msg(9)

And that's the page, bestie! 🦋 This gem lives at ./include/uapi/linux and the date on it is October 2026. Go forth and speak fluent virtio PCI device ops — periodt. 👑💖