timur.t...@gmail.com wrote on 27/03/2009 19:50:30:
>
> On Tue, Mar 24, 2009 at 6:08 PM, Joakim Tjernlund
> <joakim.tjernl...@transmode.se> wrote:
>
> > + .ndo_change_mtu = eth_change_mtu,
>
> I have an old patch for change_mtu support for ucc_geth which I've
> been meaning to push upstream. This patch uses this function instead
> of eth_change_mtu():
>
> +static int ucc_geth_change_mtu(struct net_device *dev, int new_mtu)
> +{
> + int max_rx_buf_length;
> + struct ucc_geth_private *ugeth = netdev_priv(dev);
> + int frame_size = new_mtu + 18;
> + struct ucc_geth_info *ug_info;
> + struct ucc_fast_info *uf_info;
> +
> + if (ugeth->p_rx_glbl_pram) {
> + printk("%s: Interface is active!\n", __FUNCTION__);
> + } else {
> +
> + ug_info = ugeth->ug_info;
> + uf_info = &ug_info->uf_info;
> +
> + if ((frame_size < 64) || (frame_size > JUMBO_FRAME_SIZE)) {
> + printk(KERN_ERR "%s: Invalid MTU setting\n", dev->name);
> + return -EINVAL;
> + }
> +
> + max_rx_buf_length =
> + (frame_size & ~(UCC_GETH_MRBLR_ALIGNMENT - 1)) +
> + UCC_GETH_MRBLR_ALIGNMENT;
> +
> + ugeth->ug_info->uf_info.max_rx_buf_length = max_rx_buf_length;
> + dev->mtu = new_mtu;
> +
> + /* Set the max. rx buffer size (MRBLR) */
> + uf_info->max_rx_buf_length = max_rx_buf_length;
> +
> + /* set the max. frame length (MFLR) */
> + ug_info->maxFrameLength = frame_size;
> +
> + ugeth_info("%s: MTU = %d (frame size=%d)\n", dev->name,
> + dev->mtu, frame_size);
> + }
> + return 0;
> +}
>
> Do you think this is how it should be done? I don't know enough about
> ucc_geth and MTUs to know off-hand.
Not quite so. I don't think you can support JUMBO frames with just one big
RX buffer.
Also, maxframe & RX buffer should be somewhat bigger than the actual mtu
so you can
support VLAN(4) and PPPOE(8) = 12 bytes.
You need to add 12 bytes to the default values too.
Jocke
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