virtio: Add helper functions to attach/detach vring descriptors

Move the attach and detach logic for manipulating vring descriptors
out into their own functions so that we can later extend these to
bounce the data for devices with VIRTIO_F_IOMMU_PLATFORM set.

Signed-off-by: Will Deacon <willdeacon@google.com>
[ Paul: pick from the Android tree. Rebase to the upstream ]
Signed-off-by: Ying-Chun Liu (PaulLiu) <paul.liu@linaro.org>
Cc: Bin Meng <bmeng.cn@gmail.com>
Link: https://android.googlesource.com/platform/external/u-boot/+/f73258a4bfe968c5f935db45f2ec5cc0104ee796
Reviewed-by: Simon Glass <sjg@chromium.org>

diff --git a/drivers/virtio/virtio_ring.c b/drivers/virtio/virtio_ring.c
index 5aeb13f..1bd19ad 100644 (file)
--- a/drivers/virtio/virtio_ring.c
+++ b/drivers/virtio/virtio_ring.c
@@ -47,6 +47,10 @@ static unsigned int virtqueue_attach_desc(struct virtqueue *vq, unsigned int i,
        return desc_shadow->next;
 }
 
+static void virtqueue_detach_desc(struct virtqueue *vq, unsigned int idx)
+{
+}
+
 int virtqueue_add(struct virtqueue *vq, struct virtio_sg *sgs[],
                  unsigned int out_sgs, unsigned int in_sgs)
 {
@@ -165,10 +169,12 @@ static void detach_buf(struct virtqueue *vq, unsigned int head)
        i = head;
 
        while (vq->vring_desc_shadow[i].flags & VRING_DESC_F_NEXT) {
+               virtqueue_detach_desc(vq, i);
                i = vq->vring_desc_shadow[i].next;
                vq->num_free++;
        }
 
+       virtqueue_detach_desc(vq, i);
        vq->vring_desc_shadow[i].next = vq->free_head;
        vq->free_head = head;