Re: [RFC] usbnet: use eth%d name for known ethernet devices

Arnd Bergmann
2011-03-25T16:44:10Z

On Friday 25 March 2011, Alexey Orishko wrote:
> On Fri, Mar 25, 2011 at 12:57 PM, Arnd Bergmann <arnd@arndb.de> wrote:
> >
> > That would be a different way of looking at it. FLAG_POINTTOPOINT
> > describes what the device is (a USB cable connecting two hosts), and
> > that flag can be used for various things, where the only thing
> > we currently do is the netif naming.
> >
>
> For example, cdc_ether and cdc-ncm drivers can be used in different use cases:
> a) when device terminates the IP traffic
> or
> b) where device is a wireless router.
>
> In both cases ethernet frames are sent over usb cable and terminated
> in device (eth header stripped), so it is point-to-point link for ethernet, but
> looking from IP layer is not p2p link for case b).
>
> Please, explain, based on your idea, do we set this flag in both cases or not?
> Do you want to use the same netif name for both use cases described above?
>

Most importantly, I want to keep the current rules, so that nothing breaks
for existing users.

For cdc_ether and cdc-ncm devices, my patch always sets both FLAG_ETHER and
FLAG_POINTTOPOINT, because the driver has no way to find out which of the
two is actually there.

The usb-net core driver interprets this as meaning that it has to decide
for the name based on something else, and that happens to be the presence
of a globally assigned MAC address. I don't think that keying off the MAC
address here is a particularly good idea, but that's what the driver has
always done.

Arnd