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/* This header, excluding the #ifdef __KERNEL__ part, is BSD licensed so
* anyone can use the definitions to implement compatible drivers/servers. */
/* Virtio devices use a standardized configuration space to define their
* features and pass configuration information, but each implementation can
* store and access that space differently. */
#include <linux/types.h>
/* Status byte for guest to report progress, and synchronize features. */
/* We have seen device and processed generic fields (VIRTIO_CONFIG_F_VIRTIO) */
/* We have found a driver for the device. */
/* Driver has used its parts of the config, and is happy */
/* We've given up on this device. */
/* Some virtio feature bits (currently bits 28 through 31) are reserved for the
* transport being used (eg. virtio_ring), the rest are per-device feature
* bits. */
/* Do we get callbacks when the ring is completely used, even if we've
* suppressed them? */
#ifdef __KERNEL__
#include <linux/err.h>
#include <linux/virtio.h>
* virtio_config_ops - operations for configuring a virtio device
* @get: read the value of a configuration field
* 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
* @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
* @request_vqs: request the specified number of virtqueues
* vdev: the virtio_device
* max_vqs: the max number of virtqueues we want
* If supplied, must call before any virtqueues are instantiated.
* To modify the max number of virtqueues after request_vqs has been
* called, call free_vqs and then request_vqs with a new value.
* @free_vqs: cleanup resources allocated by request_vqs
* vdev: the virtio_device
* If supplied, must call after all virtqueues have been deleted.
* @reset: reset the device
* vdev: the virtio device
* After this, status and feature negotiation must be done again
* @find_vqs: find virtqueues and instantiate them.
* vdev: the virtio_device
* nvqs: the number of virtqueues to find
* vqs: on success, includes new virtqueues
* callbacks: array of callbacks, for each virtqueue
* names: array of virtqueue names (mainly for debugging)
* Returns 0 on success or error status
* @del_vqs: free virtqueues found by find_vqs().
* @get_features: get the array of feature bits for this device.
* vdev: the virtio_device
* Returns the first 32 feature bits (all we currently need).
* @finalize_features: confirm what device features we'll be using.
* vdev: the virtio_device
* This gives the final feature bits for the device: it can change
* the dev->feature bits if it wants.
typedef void vq_callback_t(struct virtqueue *);
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);
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 *, unsigned nvqs,
struct virtqueue *vqs[],
vq_callback_t *callbacks[],
const char *names[]);
void (*del_vqs)(struct virtio_device *);
u32 (*get_features)(struct virtio_device *vdev);
void (*finalize_features)(struct virtio_device *vdev);
/* If driver didn't advertise the feature, it will never appear. */
void virtio_check_driver_offered_feature(const struct virtio_device *vdev,
unsigned int fbit);
* virtio_has_feature - helper to determine if this device has this feature.
* @vdev: the device
* @fbit: the feature bit
static inline bool virtio_has_feature(const struct virtio_device *vdev,
unsigned int fbit)
/* Did you forget to fix assumptions on max features? */
MAYBE_BUILD_BUG_ON(fbit >= 32);
virtio_check_driver_offered_feature(vdev, fbit);
return test_bit(fbit, vdev->features);
* virtio_config_val - look for a feature and get a virtio config entry.
* @vdev: the virtio device
* @fbit: the feature bit
* @offset: the type to search for.
* @val: a pointer to the value to fill in.
* The return value is -ENOENT if the feature doesn't exist. Otherwise
* the config value is copied into whatever is pointed to by v. */
#define virtio_config_val(vdev, fbit, offset, v) \
virtio_config_buf((vdev), (fbit), (offset), (v), sizeof(*v))
static inline int virtio_config_buf(struct virtio_device *vdev,
unsigned int fbit,
unsigned int offset,
void *buf, unsigned len)
if (!virtio_has_feature(vdev, fbit))
return -ENOENT;
vdev->config->get(vdev, offset, buf, len);
return 0;
static inline
struct virtqueue *virtio_find_single_vq(struct virtio_device *vdev,
vq_callback_t *c, const char *n)
vq_callback_t *callbacks[] = { c };
const char *names[] = { n };
struct virtqueue *vq;
int err = vdev->config->find_vqs(vdev, 1, &vq, callbacks, names);
if (err < 0)
return ERR_PTR(err);
return vq;
#endif /* __KERNEL__ */