On 2/28/2022 6:17 PM, James Prestwood wrote:
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.
There is no easy answer to that. It really depends on the device/firmware. To be honest I don't know if the older chips can support it. Need to check that.
What device are you specifically looking at? Regards, Arend
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