Hi Alvin, On Sat, 2022-02-26 at 11:27 +0000, Alvin Šipraga wrote: > Hi James, > > James Prestwood <prestwoj@xxxxxxxxx> writes: > > > Hi Alvin, > > > > On Fri, 2022-02-25 at 22:55 +0000, Alvin Šipraga wrote: > > > Hi James, > > > > > > James Prestwood <prestwoj@xxxxxxxxx> writes: > > > > > > > This driver does not advertise this feature yet scanning with > > > > on an > > > > AP interface appears to work just fine. > > > > --- > > > > drivers/net/wireless/broadcom/brcm80211/brcmfmac/cfg80211.c | > > > > 2 ++ > > > > 1 file changed, 2 insertions(+) > > > > > > > > I've submitted this patch mainly to start a discussion about > > > > it. I > > > > find it hard to believe that ALL brcmfmac devices support AP > > > > scanning > > > > in which case this feature needs to be limited to those devices > > > > only. Trouble is there is no FW feature for AP scanning AFAIK. > > > > > > > > In any case I think this driver needs to sort out if it > > > > supports > > > > this > > > > feature or not, and advertise as such rather than leaving > > > > userspace > > > > in the dark. > > > > > > By the way, what are the typical use-cases for AP scanning? > > > > > > I know that hostapd does a passive scan on the AP interface on > > > the > > > assumption that the driver/firmware will gather channel survey > > > data, > > > but > > > that's not a universally applicable assumption. Not all > > > implementations > > > will do that. > > > > We have someone wanting it for onboarding/configuring a new > > headless > > device. Where on boot, if it is unconfigured, it starts an AP and > > waits > > for a client to configure it. > > > > A client would connect, have the device scan and present available > > networks. The client then selects a network and provides > > credentials. > > The new device can then switch back to station mode and connect. > > > > This is a relatively common practice I've seen with IoT devices. > > Ah OK! Actually we do pretty much the same here at B&O with > brcmfmac. But rather than starting the AP on the primary interface > (the > one default created by the driver), we add a separate AP interface > with > the equivalent of the following command: > > # iw dev wlan0 add uap0 type __ap > > Here wlan0 is the primary interface, and uap0 is what I call my AP. > > In that case you can start the AP on uap0, but still do scanning on > wlan0 (which remains in station mode). Don't quote me on it, but I > think > this is the canonical approach with this driver. Is it something you > have considered? Thanks, this does seem to work on brcmfmac. I had tried this on other hardware without any luck. I mentioned this to the user but since the AP scanning feature has been implemented they may want to still use that, but who knows. I think finding out if brcmfmac is intended to scan on the AP interface would still be good to know. > > > > Other than this I cant see much else of a use case besides, like > > you > > mentioned, gathering survey data to choose a low load channel (ACS > > its > > called I think?) > > Yes, see hostap/src/ap/acs.c. > > See also > https://lore.kernel.org/linux-wireless/96652669-0cad-8cdb-fbe1-4df0f7161102@xxxxxxxxxxxxxxx/ > for some grumblings of mine on this API. > > > > > Sadly this onboarding use case is quite perfect for DPP, but since > > Apple came up with their own protocol DPP won't work for any > > products > > that want cross compatibility... > > Yes, this is a real shame. And I highly doubt that Apple will abandon > their own protocol. > > > > > > > > > Kind regards, > > > Alvin > > > > > > > > > > > diff --git > > > > a/drivers/net/wireless/broadcom/brcm80211/brcmfmac/cfg80211.c > > > > b/drivers/net/wireless/broadcom/brcm80211/brcmfmac/cfg80211.c > > > > index fb727778312c..b6a50e65dbf6 100644 > > > > --- > > > > a/drivers/net/wireless/broadcom/brcm80211/brcmfmac/cfg80211.c > > > > +++ > > > > b/drivers/net/wireless/broadcom/brcm80211/brcmfmac/cfg80211.c > > > > @@ -7729,6 +7729,8 @@ struct brcmf_cfg80211_info > > > > *brcmf_cfg80211_attach(struct brcmf_pub *drvr, > > > > #endif > > > > } > > > > > > > > + wiphy->features |= NL80211_FEATURE_AP_SCAN; > > > > + > > > > return cfg; > > > > > > > > detach:
