RDMA/uverbs: Implement an ioctl that can call write and write_ex handlers

Now that the handlers do not process their own udata we can make a
sensible ioctl that wrappers them. The ioctl follows the same format as
the write_ex() and has the user explicitly specify the core and driver
in/out opaque structures and a command number.

This works for all forms of write commands.

Signed-off-by: Jason Gunthorpe <jgg@mellanox.com>
Signed-off-by: Leon Romanovsky <leonro@mellanox.com>
Signed-off-by: Doug Ledford <dledford@redhat.com>

include/uapi/rdma/ib_user_ioctl_cmds.h

@@ -63,6 +63,16 @@ enum {
 	UVERBS_ATTR_UHW_OUT,
 };
 
+enum uverbs_methods_device {
+	UVERBS_METHOD_INVOKE_WRITE,
+};
+
+enum uverbs_attrs_invoke_write_cmd_attr_ids {
+	UVERBS_ATTR_CORE_IN,
+	UVERBS_ATTR_CORE_OUT,
+	UVERBS_ATTR_WRITE_CMD,
+};
+
 enum uverbs_attrs_create_cq_cmd_attr_ids {
 	UVERBS_ATTR_CREATE_CQ_HANDLE,
 	UVERBS_ATTR_CREATE_CQ_CQE,