Hi Dan, >>>> I've updated wireless code on RHEL and get complain that now >>>> cfg80211 and rfkill modules are loaded on machines that do not have >>>> wireless hardware. Modules are auto-loaded because NetworkManager send >>>> nl80211 messages to check if there are wireless devices in the system. >>>> >>>> Hence my question, can we revert commit fb4e156886ce >>>> "nl80211: Add generic netlink module alias for cfg80211/nl80211" ? >>> >>> Realistically, we can't revert it, but only remove the >>> MODULE_ALIAS_GENL_FAMILY() line. >>> >>>> Auto loading nl80211 does not seems to be necessary, if there are >>>> wireless devices nl80211 will be loaded anyway. >>> >>> Maybe other applications would like to see an empty list of devices? But >>> OTOH, if they're robust at all, they have to cope with kernels not even >>> compiled with nl80211, so I guess for me I don't really see a big >>> difference in whether the module alias exists or not. >> >> auto-loading cfg80211 module when userspace requests nl80211 netlink family >> is exactly the right thing to do. Systems compiled without nl80211 support >> and systems with no wireless device attached are two different things. >> >> Someone can fix NetworkManager to not send nl80211 messages or just plain >> accept that cfg80211 will be loaded. > > NM uses nl80211 initially to determine whether *any* ethernet-type > interface (a) is actually WiFi, and (b) should be driven by nl80211 or > WEXT. Because of the variety of drivers (both in-kernel and > out-of-kernel) and the variety of kernel versions (NM supports back to > early 3.x series) we cannot rely on specific behavior. > > So given an ethernet-type interface, how do we determine that it is > wifi? > > DEVTYPE=wlan - not always reliable due to driver and kernel versions
if anybody wants to write kernel patches, then making sure that all wireless drivers expose DEVTYPE=wlan is the way to go. If for some reason a driver does not do it, that is a bug. > "phy80211" in sysfs: same reason; also doesn't capture WEXT or > out-of-tree drivers > > nl80211 calls: this is the only 100% reliable mechanism to detect > whether an ethernet-type interface is actually WiFi and nl80211-capable. > > And unfortunately calling nl80211 loads the module... So be it then, the cfg80211 modules gets loaded. People have to live with that. And just to be clear, this is not a kernel bug. Exposing the correct module alias for its netlink family is what the module should be doing. Regards Marcel -- To unsubscribe from this list: send the line "unsubscribe linux-wireless" in the body of a message to [email protected] More majordomo info at http://vger.kernel.org/majordomo-info.html
