[PATCH rdma-next v3 1/7] RDMA/core: Add ib_no_udata_io() helper

[Jacob Moroni <jmoroni@google.com>]

In many cases, a driver op accepts no input data and provides
no response. This helper can be used in those handlers to
adhere to the uAPI forward/backward compat rules by failing
early if invalid udata is provided (whether input or output).

Signed-off-by: Jacob Moroni <jmoroni@google.com>
---
 include/rdma/uverbs_ioctl.h | 20 ++++++++++++++++++++
 1 file changed, 20 insertions(+)

diff --git a/include/rdma/uverbs_ioctl.h b/include/rdma/uverbs_ioctl.h
index 24fd36213023..80f3ba6663d0 100644
--- a/include/rdma/uverbs_ioctl.h
+++ b/include/rdma/uverbs_ioctl.h
@@ -1151,4 +1151,24 @@ static inline int ib_respond_empty_udata(struct ib_udata *udata)
 	return 0;
 }
 
+/**
+ * ib_no_udata_io - Ensure no input data and zero fill the response buffer
+ * @udata: The system call's ib_udata struct
+ *
+ * Driver ops which do not accept any input data and do not provide any response
+ * data may call this at the beginning of their handler to fully adhere to the
+ * uAPI forward/backward compatibility rules.
+ *
+ * Return: Negative failure code if the op should be denied, 0 otherwise.
+ */
+static inline int ib_no_udata_io(struct ib_udata *udata)
+{
+	int ret = ib_is_udata_in_empty(udata);
+
+	if (ret)
+		return ret;
+
+	return ib_respond_empty_udata(udata);
+}
+
 #endif
-- 
2.55.0.rc0.799.gd6f94ed593-goog