On Friday 25 March 2011, Alexey Orishko wrote: > On Fri, Mar 25, 2011 at 12:57 PM, Arnd Bergmann <arnd@xxxxxxxx> 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 -- To unsubscribe from this list: send the line "unsubscribe linux-usb" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
