Hi all, I am trying to understand parts of the net80211 subsystem and currently looking through ic->ic_parent. Please confirm my understanding of how ieee80211com's ic_parent handler is implemented by various drivers.
When is ic_parent run: * This function is called when the device goes up or down. From user-space, this would be like running `ifconfig wlan0 up` or `ifconfig wlan0 down`. The parent is the function `parent_updown`. Early Exit condition: * There is a detach if-condition that quickly exits. The exact check for this is different per driver (sc->sc_detached or sc->sc_flags), but the code checks that a flag is set in the detach handler. This step prevents trying to start/stop a VAP after the device was detached. Bringing the device up or down: * If the number of running vaps, as tracked by ic->ic_nrunning, is greater than 0 (meaning at least 1 VAP is up), then: ** There is another if-condition that if the device isn't running at all, then start all VAPs. This is done by ieee80211_start_all(). ** Otherwise, stop all VAPS. With rtwn_parent (sys/dev/rtwn/if_rtwn.c) it runs a TAILQ_FOREACH on each VAP and runs ieee80211_stop_locked on each VAP. Other drivers seem to do this slightly differently, such as rum_parent (sys/dev/usb/wlan/if_rum.c) it seems to only stop 1 VAP, which suggests to me that this device cannot support multiple VAPs * If no VAPs are running, then we stop the device. Is this accurate? What I'm confused about is: If this function is invoked when you run `ifconfig wlan0 up`, it seems that you specify a specific VAP, while all VAPs are simultaneously brought online rather than a single VAP. So its all or none? * ic->ic_parent puts the device up or down based on flags (sc_nrunning or sc_flags), but when are those flags updated in this process? Sorry for the multi-part question and thank you in advance! - Farhan
