Netgear Aircard 341U in QMI mode, switching to 802.3

[David McCullough]

Bjørn Mork wrote the following:
> David McCullough <david.mccullough at accelecon.com> writes:
> 
> > +	if (skb_headroom(skb) < ETH_HLEN) {
> > +		skb2 = skb_copy_expand(skb, ETH_HLEN, 0, GFP_ATOMIC);
> > +		if (!skb2) {
> > +			dev->net->stats.rx_errors++;
> > +			return 0;
> > +		}
> > +		skb = skb2;
> > +	}
> 
> Do you ever hit this?  Yes, I know we are not supposed to depend on the
> built-in headroom, but NET_SKB_PAD is at least 32 bytes regardless of
> platform AFAICS so this if test should never be true?
> 
> But I suppose you had your reasons to add this.  In any case, I think we
> should rather allocate the necessary headroom in the fist place if we
> are going support raw-ip.  The rx_fixup header addition was really meant
> to be an exceptional case, and not the modus operandi.  That's why I
> found it acceptable to depend on the built-in headroom.

Unfortunately I cannot recall,  given that I probably started with
qmi_wwan_rx_fixup,  but it silently fails if there is no room, my guess
is I needed to make the change,  but I cannot remember for sure :-(

> 
> > +	dev->net->mtu = 1460;
> 
> I noticed this recent discussion with interest:
> https://forum.sierrawireless.com/viewtopic.php?f=117&t=8771&sid=e4a234dd9b4f3864b46973127a705273#p35800
> 
> If we get the correct MTU from QMI, then we (that is userspace. as
> that's where we do QMI) should probably configure the netdev
> accordingly.

We are already using any MTU reported via DHCP,  the qmi version we are
running on those hosts does not support the --wds-get-current-settings option
so I cannot curently check that for you

> > +	/* Sprint 341u modem in pass through and non-pass-through modes */
> > +	{QMI_RAWIP_FIXED_INTF(0x1199,0x9057,8)},/* ippassthrough */
> > +	{QMI_RAWIP_FIXED_INTF(0x1199,0x9055,8)},/* non-passthrough */
> 
> 
> Right.  So that's the answer to the question about 9057 vs 9055, I
> guess.  Ah, I see you're already on that.

Yep,

Cheers,
Davidm

-- 
David McCullough,  david.mccullough at accelecon.com,   Ph: 0410 560 763