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

On Friday 25 March 2011, Alexey Orishko wrote:

On Fri, Mar 25, 2011 at 12:57 PM, Arnd Bergmann [off-list ref] wrote:

quoted

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