virtio: make add_buf return capacity remaining

This API change means that virtio_net can tell how much capacity
remains for buffers.  It's necessarily fuzzy, since
VIRTIO_RING_F_INDIRECT_DESC means we can fit any number of descriptors
in one, *if* we can kmalloc.

Signed-off-by: Rusty Russell <rusty@rustcorp.com.au>
Cc: Dinesh Subhraveti <dineshs@us.ibm.com>

1 files changed, 1 insertions, 1 deletions

diff --git a/drivers/char/hw_random/virtio-rng.c b/drivers/char/hw_random/virtio-rng.c
index 32216b623248..b6c24dcc987d 100644
--- a/drivers/char/hw_random/virtio-rng.c
+++ b/drivers/char/hw_random/virtio-rng.c
@@ -51,7 +51,7 @@ static void register_buffer(void)
 
         sg_init_one(&sg, random_data+data_left, RANDOM_DATA_SIZE-data_left);
         /* There should always be room for one buffer. */
-        if (vq->vq_ops->add_buf(vq, &sg, 0, 1, random_data) != 0)
+        if (vq->vq_ops->add_buf(vq, &sg, 0, 1, random_data) < 0)
                 BUG();
         vq->vq_ops->kick(vq);
 }