+static int virtio_ccw_set_transport_rev(struct virtio_ccw_device *vcdev)
+{
+ struct virtio_rev_info *rev;
+ struct ccw1 *ccw;
+ int ret;
+
+ ccw = kzalloc(sizeof(*ccw), GFP_DMA | GFP_KERNEL);
+ if (!ccw)
+ return -ENOMEM;
+ rev = kzalloc(sizeof(*rev), GFP_DMA | GFP_KERNEL);
+ if (!rev) {
+ kfree(ccw);
+ return -ENOMEM;
+ }
+
+ /* Set transport revision */
+ ccw->cmd_code = CCW_CMD_SET_VIRTIO_REV;
+ ccw->flags = 0;
+ ccw->count = sizeof(*rev);
+ ccw->cda = (__u32)(unsigned long)rev;
+
+ vcdev->revision = VIRTIO_CCW_REV_MAX;
+ do {
+ rev->revision = vcdev->revision;
+ /* none of our supported revisions carry payload */
+ rev->length = 0;
+ ret = ccw_io_helper(vcdev, ccw,
+ VIRTIO_CCW_DOING_SET_VIRTIO_REV);
+ if (ret == -EOPNOTSUPP) {
+ if (vcdev->revision == 0)
+ /*
+ * The host device does not support setting
+ * the revision: let's operate it in legacy
+ * mode.
+ */
+ ret = 0;
+ else
+ vcdev->revision--;
+ }
+ } while (ret == -EOPNOTSUPP);
+
+ kfree(ccw);
+ kfree(rev);
+ return ret;
+}