diff --git a/drivers/net/wireless/prism54/isl_ioctl.c b/drivers/net/wireless/prism54/isl_ioctl.c
index 97fa14e0a47912c0c8513a23dd8053b3acb649bc..3d75a7137d3cccb41f0533144c88c81a3833963a 100644
--- a/drivers/net/wireless/prism54/isl_ioctl.c
+++ b/drivers/net/wireless/prism54/isl_ioctl.c
@@ -2518,7 +2518,7 @@ enum {
 
 #define PRISM2_HOSTAPD_MAX_BUF_SIZE 1024
 #define PRISM2_HOSTAPD_GENERIC_ELEMENT_HDR_LEN \
-((int) (&((struct prism2_hostapd_param *) 0)->u.generic_elem.data))
+	offsetof(struct prism2_hostapd_param, u.generic_elem.data)
 
 /* Maximum length for algorithm names (-1 for nul termination)
  * used in ioctl() */