MT_SKEY_MODE_SHIFT
val &= ~(MT_SKEY_MODE_MASK << MT_SKEY_MODE_SHIFT(vif_idx, key_idx));
val |= cipher << MT_SKEY_MODE_SHIFT(vif_idx, key_idx);
val &= ~(MT_SKEY_MODE_MASK << MT_SKEY_MODE_SHIFT(vif_idx, key_idx));
val |= cipher << MT_SKEY_MODE_SHIFT(vif_idx, key_idx);