+/*
+ * calculate actual hardware mtu
+ */
+static int compute_hw_mtu(struct bcm_enet_priv *priv, int mtu)
+{
+ int actual_mtu;
+
+ actual_mtu = mtu;
+
+ /* add ethernet header + vlan tag size */
+ actual_mtu += VLAN_ETH_HLEN;
+
+ if (actual_mtu < 64 || actual_mtu > BCMENET_MAX_MTU)
+ return -EINVAL;
+
+ /*
+ * setup maximum size before we get overflow mark in
+ * descriptor, note that this will not prevent reception of
+ * big frames, they will be split into multiple buffers
+ * anyway
+ */
+ priv->hw_mtu = actual_mtu;
+
+ /*
+ * align rx buffer size to dma burst len, account FCS since
+ * it's appended
+ */
+ priv->rx_skb_size = ALIGN(actual_mtu + ETH_FCS_LEN,
+ BCMENET_DMA_MAXBURST * 4);
+ return 0;
+}
+
+/*
+ * adjust mtu, can't be called while device is running
+ */
+static int bcm_enet_change_mtu(struct net_device *dev, int new_mtu)
+{
+ int ret;
+
+ if (netif_running(dev))
+ return -EBUSY;
+
+ ret = compute_hw_mtu(netdev_priv(dev), new_mtu);
+ if (ret)
+ return ret;
+ dev->mtu = new_mtu;
+ return 0;
+}
+