STRUCT VIRTIO_CONFIG_OPS(9)

🦋 struct virtio_config_ops(9) 🦋

okay bestie, welcome to the Kernel API Manual page for struct virtio_config_ops — yes it's a whole struct of function pointers and yes it's lowkey the main character of virtio device configuration. grab a strawberry drink, we're doing this 💅

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✨ NAME ✨

struct virtio_config_ops — operations for configuring a virtio device 🎀

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🌸 SYNOPSIS 🌸

struct virtio_config_ops {
    void (*get)(struct virtio_device *vdev, unsigned offset, void *buf,
unsigned len);
    void (*set)(struct virtio_device *vdev, unsigned offset, const void
*buf, unsigned len);
    u32 (*generation)(struct virtio_device *vdev);
    u8 (*get_status)(struct virtio_device *vdev);
    void (*set_status)(struct virtio_device *vdev, u8 status);
    void (*reset)(struct virtio_device *vdev);
    int (*find_vqs)(struct virtio_device *vdev, unsigned int nvqs,
struct virtqueue *vqs[], struct virtqueue_info vqs_info[], struct
irq_affinity *desc);
    void (*del_vqs)(struct virtio_device *);
    void (*synchronize_cbs)(struct virtio_device *);
    u64 (*get_features)(struct virtio_device *vdev);
    void (*get_extended_features)(struct virtio_device *vdev, u64
*features);
    int (*finalize_features)(struct virtio_device *vdev);
    const char *(*bus_name)(struct virtio_device *vdev);
    int (*set_vq_affinity)(struct virtqueue *vq, const struct cpumask
*cpu_mask);
    const struct cpumask *(*get_vq_affinity)(struct virtio_device *vdev,
int index);
    bool (*get_shm_region)(struct virtio_device *vdev, struct
virtio_shm_region *region, u8 id);
    int (*disable_vq_and_reset)(struct virtqueue *vq);
    int (*enable_vq_after_reset)(struct virtqueue *vq);
 };

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💜 Members 💜

• get — read the value of a configuration field, fr fr. vdev: the virtio_device. offset: the offset of the configuration field. buf: the buffer to write the field value into. len: the length of the buffer. 🫶
• set — write the value of a configuration field. vdev: the virtio_device. offset: the offset of the configuration field. buf: the buffer to read the field value from. len: the length of the buffer. ✨
• generation — config generation counter, and it's optional btw. vdev: the virtio_device. Returns the config generation counter. ⭐
• get_status — read the status byte. vdev: the virtio_device. Returns the status byte. 🦋
• set_status — write the status byte. vdev: the virtio_device. status: the new status byte. 💅
• reset — reset the device. vdev: the virtio device. After this, status and feature negotiation must be done again. And listen 👑: the device must not be reset from its vq/config callbacks, or in parallel with being added/removed. like, do not do that.
• find_vqs — find virtqueues and instantiate them, iconic behaviour honestly. vdev: the virtio_device. nvqs: the number of virtqueues to find. vqs: on success, includes new virtqueues. vqs_info: array of virtqueue_info structures. Returns 0 on success or error status. 💖
• del_vqs — free virtqueues found by find_vqs, the cleanup arc 🧹
• synchronize_cbs — synchronize with the virtqueue callbacks (optional!). The function guarantees that all memory operations on the queue before it are visible to the vring_interrupt that is called after it. vdev: the virtio_device. 🌈
• get_features — get the array of feature bits for this device. vdev: the virtio_device. Returns the first 64 feature bits. 🔥
• get_extended_features — vdev: the virtio_device. Returns the first VIRTIO_FEATURES_BITS feature bits (all we currently need). ngl, that's the vibe.
• finalize_features — confirm what device features we'll be using. vdev: the virtio_device. This sends the driver feature bits to the device: it can change the dev->feature bits if it wants. Note that despite the name this can be called any number of times. Returns 0 on success or error status. 🙈
• bus_name — return the bus name associated with the device (optional). vdev: the virtio_device. This returns a pointer to the bus name a la pci_name from which the caller can then copy. 🎀
• set_vq_affinity — set the affinity for a virtqueue (optional). 💫
• get_vq_affinity — get the affinity for a virtqueue (optional). 💫
• get_shm_region — get a shared memory region based on the index. 🌸
• disable_vq_and_reset — reset a queue individually (optional). vq: the virtqueue. Returns 0 on success or error status. disable_vq_and_reset will guarantee that the callbacks are disabled and synchronized. Except for the callback, the caller should guarantee that the vring is not accessed by any functions of virtqueue. 🫡
• enable_vq_after_reset — enable a reset queue. vq: the virtqueue. Returns 0 on success or error status. If disable_vq_and_reset is set, then enable_vq_after_reset must also be set — they're a package deal bestie, no cap. 💀

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⭐ Note ⭐

Do not assume that a transport implements all of the operations getting/setting a value as a simple read/write! Generally speaking, any of get/set, get_status/set_status, or get_features/finalize_features are NOT safe to be called from an atomic context. 😭 read that again. it's giving "danger", it's giving "respect the caveat".

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🌈 SEE ALSO 🌈

Kernel file ./include/linux/virtio_config.h — plus these besties: struct virtqueue_info(9), struct virtio_map_ops(9), __virtio_test_bit(9), __virtio_set_bit(9), __virtio_clear_bit(9), virtio_has_feature(9), virtio_has_dma_quirk(9), virtio_synchronize_cbs(9), virtio_device_ready(9), virtqueue_set_affinity(9).

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okay that's the whole page, you ate that 💅 this was served fresh from ./include/linux, dated October 2026, in the struct virtio_config_ops(9) era — mwah, go read the source, ily, bye 🎀🦋💖