1 /*-
2  * SPDX-License-Identifier: BSD-3-Clause
38 /* This marks a buffer as write-only (otherwise read-only). */
43 /* The Host uses this in used->flags to advise the Guest: don't kick me
47 /* The Guest uses this in avail->flags to advise the Host: don't
55         /* Address (guest-physical). */
71 /* uint32_t is used here for ids for padding reasons. */
86 	unsigned int num;  member
94  * When using pre-virtio 1.0 layout, these fall out naturally.
101  * looks like this.  We assume num is a power of 2.
105  *      struct vring_desc desc[num];
107  *      // A ring of available descriptor heads with free-running index.
110  *      __u16 available[num];
116  *      // A ring of used descriptor heads with free-running index.
119  *      struct vring_used_elem used[num];
130 #define vring_used_event(vr)	((vr)->avail->ring[(vr)->num])
131 #define vring_avail_event(vr)	(*(uint16_t *)&(vr)->used->ring[(vr)->num])
134 vring_size(unsigned int num, unsigned long align)  in vring_size()  argument
138 	size = num * sizeof(struct vring_desc);  in vring_size()
139 	size += sizeof(struct vring_avail) + (num * sizeof(uint16_t)) +  in vring_size()
141 	size = (size + align - 1) & ~(align - 1);  in vring_size()
143 	    (num * sizeof(struct vring_used_elem)) + sizeof(uint16_t);  in vring_size()
148 vring_init(struct vring *vr, unsigned int num, uint8_t *p,  in vring_init()  argument
151         vr->num = num;  in vring_init()
152         vr->desc = (struct vring_desc *) p;  in vring_init()
153         vr->avail = (struct vring_avail *) (p +  in vring_init()
154 	    num * sizeof(struct vring_desc));  in vring_init()
155         vr->used = (void *)  in vring_init()
156 	    (((unsigned long) &vr->avail->ring[num] + align-1) & ~(align-1));  in vring_init()
170 	return (uint16_t)(new_idx - event_idx - 1) < (uint16_t)(new_idx - old);  in vring_need_event()