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#ifndef _LINUX_VIRTIO_RING_H
#define _LINUX_VIRTIO_RING_H
/* An interface for efficient virtio implementation, currently for use by KVM
* and lguest, but hopefully others soon. Do NOT change this since it will
* break existing servers and clients.
*
* This header is BSD licensed so anyone can use the definitions to implement
* compatible drivers/servers.
*
* Copyright Rusty Russell IBM Corporation 2007. */
#include <linux/types.h>
/* This marks a buffer as continuing via the next field. */
#define VRING_DESC_F_NEXT 1
/* This marks a buffer as write-only (otherwise read-only). */
#define VRING_DESC_F_WRITE 2
/* The Host uses this in used->flags to advise the Guest: don't kick me when
* you add a buffer. It's unreliable, so it's simply an optimization. Guest
* will still kick if it's out of buffers. */
#define VRING_USED_F_NO_NOTIFY 1
/* The Guest uses this in avail->flags to advise the Host: don't interrupt me
* when you consume a buffer. It's unreliable, so it's simply an
* optimization. */
#define VRING_AVAIL_F_NO_INTERRUPT 1
/* Virtio ring descriptors: 16 bytes. These can chain together via "next". */
struct vring_desc
{
/* Address (guest-physical). */
__u64 addr;
/* Length. */
__u32 len;
/* The flags as indicated above. */
__u16 flags;
/* We chain unused descriptors via this, too */
__u16 next;
};
struct vring_avail
{
__u16 flags;
__u16 idx;
__u16 ring[];
};
/* u32 is used here for ids for padding reasons. */
struct vring_used_elem
{
/* Index of start of used descriptor chain. */
__u32 id;
/* Total length of the descriptor chain which was used (written to) */
__u32 len;
};
struct vring_used
{
__u16 flags;
__u16 idx;
struct vring_used_elem ring[];
};
struct vring {
unsigned int num;
struct vring_desc *desc;
struct vring_avail *avail;
struct vring_used *used;
};
/* The standard layout for the ring is a continuous chunk of memory which looks
* like this. We assume num is a power of 2.
*
* struct vring
* {
* // The actual descriptors (16 bytes each)
* struct vring_desc desc[num];
*
* // A ring of available descriptor heads with free-running index.
* __u16 avail_flags;
* __u16 avail_idx;
* __u16 available[num];
*
* // Padding to the next align boundary.
* char pad[];
*
* // A ring of used descriptor heads with free-running index.
* __u16 used_flags;
* __u16 used_idx;
* struct vring_used_elem used[num];
* };
*/
static inline void vring_init(struct vring *vr, unsigned int num, void *p,
unsigned long align)
{
vr->num = num;
vr->desc = p;
vr->avail = p + num*sizeof(struct vring_desc);
vr->used = (void *)(((unsigned long)&vr->avail->ring[num] + align-1)
& ~(align - 1));
}
static inline unsigned vring_size(unsigned int num, unsigned long align)
{
return ((sizeof(struct vring_desc) * num + sizeof(__u16) * (2 + num)
+ align - 1) & ~(align - 1))
+ sizeof(__u16) * 2 + sizeof(struct vring_used_elem) * num;
}
#ifdef __KERNEL__
#include <linux/irqreturn.h>
struct virtio_device;
struct virtqueue;
struct virtqueue *vring_new_virtqueue(unsigned int num,
struct virtio_device *vdev,
void *pages,
void (*notify)(struct virtqueue *vq),
void (*callback)(struct virtqueue *vq));
void vring_del_virtqueue(struct virtqueue *vq);
/* Filter out transport-specific feature bits. */
void vring_transport_features(struct virtio_device *vdev);
irqreturn_t vring_interrupt(int irq, void *_vq);
#endif /* __KERNEL__ */
#endif /* _LINUX_VIRTIO_RING_H */
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