Optimizations for qmi_wwan.c

[Dan Williams]

On Tue, 2019-09-24 at 20:38 +0200, Markus Gothe wrote:
> I doubt it is the correct list, but I am giving it a try. At least it
> is related.
> 
> Today I realized the "raw ip" mode got merged a few years ago. Geesh,
> I am getting old.
> 
> However there are some drawbacks with the implementation 1) a boolean
> mode of operation (instead of a tristate with fake MAC layer) 2)
> branching in the rx_fixup.
> 
> Since one cannot change the mode of operation when the device is up
> and running (at least I couldn't), this seems to be the perfect place
> to use "static keys" a.k.a. "jump labels" a.k.a. memory patching code
> as outlined here 
> https://www.kernel.org/doc/Documentation/static-keys.txt
> 
> Pros? Speed ofc... Cons? If the architecture doesn't implement it
> correctly things might fail.
> 
> To address the 1) is easy and I sent a separate driver that did fake
> the MAC layer here some years ago.

Do you mean keep the device in raw_ip mode (since most recent devices
don't support the old 802.3 mode), but have the driver fake the MAC and
operate like the old "802.3" as Linux/userspace sees it?

What applications actually care about L2 Ethernet MAC addresses and
don't work with raw-ip mode?

Dan