IB/uverbs: Allow resize CQ operation to return driver-specific data

Add a ib_uverbs_resize_cq_resp.driver_data field so that low-level
drivers can return data from a resize CQ operation to userspace.  Have
ib_uverbs_resize_cq() only copy the cqe field, to avoid having to bump
the userspace ABI.
Signed-off-by: Ralph Campbell <ralph.campbell@qlogic.com>
Signed-off-by: Roland Dreier <rolandd@cisco.com>

drivers/infiniband/core/uverbs_cmd.c

@@ -879,11 +879,10 @@ ssize_t ib_uverbs_resize_cq(struct ib_uverbs_file *file,
 	if (ret)
 		goto out;
 
-	memset(&resp, 0, sizeof resp);
 	resp.cqe = cq->cqe;
 
 	if (copy_to_user((void __user *) (unsigned long) cmd.response,
-			 &resp, sizeof resp))
+			 &resp, sizeof resp.cqe))
 		ret = -EFAULT;
 
 out:

include/rdma/ib_user_verbs.h

@@ -275,6 +275,8 @@ struct ib_uverbs_resize_cq {
 
 struct ib_uverbs_resize_cq_resp {
 	__u32 cqe;
+	__u32 reserved;
+	__u64 driver_data[0];
 };
 
 struct ib_uverbs_poll_cq {