STRUCT VFIO_DEVICE_OPS(9)

💅 struct vfio_device_ops(9) 💅

okay so bestie, we're in the Kernel API Manual, section 9, and today's main character is struct vfio_device_ops — the VFIO bus driver device callbacks. this is the vibe check page for anyone writing a VFIO bus driver, so grab a snack 🍓 and let's get into it ✨

🌸 NAME 🌸

struct vfio_device_ops — VFIO bus driver device callbacks 🦋

✨ SYNOPSIS ✨

struct vfio_device_ops {
    char *name;
    int (*init)(struct vfio_device *vdev);
    void (*release)(struct vfio_device *vdev);
    int (*bind_iommufd)(struct vfio_device *vdev, struct iommufd_ctx *ictx, u32 *out_device_id);
    void (*unbind_iommufd)(struct vfio_device *vdev);
    int (*attach_ioas)(struct vfio_device *vdev, u32 *pt_id);
    void (*detach_ioas)(struct vfio_device *vdev);
    int (*pasid_attach_ioas)(struct vfio_device *vdev, u32 pasid, u32 *pt_id);
    void (*pasid_detach_ioas)(struct vfio_device *vdev, u32 pasid);
    int (*open_device)(struct vfio_device *vdev);
    void (*close_device)(struct vfio_device *vdev);
    ssize_t (*read)(struct vfio_device *vdev, char __user *buf, size_t count, loff_t *ppos);
    ssize_t (*write)(struct vfio_device *vdev, const char __user *buf, size_t count, loff_t *size);
    long (*ioctl)(struct vfio_device *vdev, unsigned int cmd, unsigned long arg);
    int (*get_region_info_caps)(struct vfio_device *vdev, struct vfio_region_info *info, struct vfio_info_cap *caps);
    int (*mmap)(struct vfio_device *vdev, struct vm_area_struct *vma);
    void (*request)(struct vfio_device *vdev, unsigned int count);
    int (*match)(struct vfio_device *vdev, char *buf);
    int (*match_token_uuid)(struct vfio_device *vdev, const uuid_t *uuid);
    void (*dma_unmap)(struct vfio_device *vdev, u64 iova, u64 length);
    int (*device_feature)(struct vfio_device *device, u32 flags, void __user *arg, size_t argsz);
};

🫶 Members 🫶

• name — Name of the device driver. that's it, that's the whole job 💜
• init — initialize private fields in device structure
• release — Reclaim private fields in device structure
• bind_iommufd — Called when binding the device to an iommufd
• unbind_iommufd — Opposite of bind_iommufd
• attach_ioas — Called when attaching device to an IOAS/HWPT managed by the bound iommufd. Undo in unbind_iommufd if detach_ioas is not called. 👀 yes the "undo" note is load-bearing, don't skip it
• detach_ioas — Opposite of attach_ioas
• pasid_attach_ioas — The pasid variation of attach_ioas
• pasid_detach_ioas — Opposite of pasid_attach_ioas
• open_device — Called when the first file descriptor is opened for this device
• close_device — Opposite of open_device
• read — Perform read(2) on device file descriptor
• write — Perform write(2) on device file descriptor
• ioctl — Perform ioctl(2) on device file descriptor, supporting VFIO_DEVICE_* operations documented below
• mmap — Perform mmap(2) on a region of the device file descriptor
• request — Request for the bus driver to release the device
• match — Optional device name match callback (return: 0 for no-match, >0 for match, -errno for abort (ex. match with insufficient or incorrect additional args) 🔥 like, read the return contract twice, it's giving "0 means nope"
• match_token_uuid — Optional device token match/validation. Return 0 if the uuid is valid for the device, -errno otherwise. uuid is NULL if none was provided.
• dma_unmap — Called when userspace unmaps IOVA from the container this device is attached to.
• device_feature — Optional, fill in the VFIO_DEVICE_FEATURE ioctl

and yeah — get_region_info_caps is sitting right there in the struct up top, but this page doesn't give it its own little blurb, so I'm not out here making one up 😌 no cap.

👑 SEE ALSO 👑

Kernel file ./include/linux/vfio.h struct vfio_migration_ops(9), struct vfio_log_ops(9), vfio_check_feature(9), vfio_check_precopy_ioctl(9) 🦋

okay that's the whole page, bestie, you ate that 💅✨ this cutie dropped from ./include/linux, version date October 2026 — go forth and write iconic callbacks, periodt 🌈🎀