This function is returning pointers.  Sparse complains here:
drivers/acpi/apei/einj.c:262:32: warning:
	Using plain integer as NULL pointer
Signed-off-by: Dan Carpenter <dan.carpenter@oracle.com>
Acked-by: Huang Ying <ying.huang@intel.com>
Signed-off-by: Len Brown <len.brown@intel.com>
 
                v4param = ioremap(paddrv4, sizeof(*v4param));
                if (!v4param)
-                       return 0;
+                       return NULL;
                if (readq(&v4param->reserved1) || readq(&v4param->reserved2)) {
                        iounmap(v4param);
-                       return 0;
+                       return NULL;
                }
                return v4param;
        }
 
-       return 0;
+       return NULL;
 }
 
 /* do sanity check to trigger table */