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, 2 insertions, 2 deletions

diff --git a/drivers/char/virtio_console.c b/drivers/char/virtio_console.c
index c74dacfa6795..a035ae39a359 100644
--- a/drivers/char/virtio_console.c
+++ b/drivers/char/virtio_console.c
@@ -65,7 +65,7 @@ static int put_chars(u32 vtermno, const char *buf, int count)
 
         /* add_buf wants a token to identify this buffer: we hand it any
          * non-NULL pointer, since there's only ever one buffer. */
-        if (out_vq->vq_ops->add_buf(out_vq, sg, 1, 0, (void *)1) == 0) {
+        if (out_vq->vq_ops->add_buf(out_vq, sg, 1, 0, (void *)1) >= 0) {
                 /* Tell Host to go! */
                 out_vq->vq_ops->kick(out_vq);
                 /* Chill out until it's done with the buffer. */
@@ -85,7 +85,7 @@ static void add_inbuf(void)
         sg_init_one(sg, inbuf, PAGE_SIZE);
 
         /* We should always be able to add one buffer to an empty queue. */
-        if (in_vq->vq_ops->add_buf(in_vq, sg, 0, 1, inbuf) != 0)
+        if (in_vq->vq_ops->add_buf(in_vq, sg, 0, 1, inbuf) < 0)
                 BUG();
         in_vq->vq_ops->kick(in_vq);
 }