Re: [PATCH] scan: limit COLOCATED_6GHZ flag to 6ghz devices

James Prestwood
2024-01-03T12:58:44Z

Hi Keith,

On 1/3/24 4:56 AM, James Prestwood wrote:
> It was seen that this flag seems to cause issues when in AP mode on
> brcmfmac devices (e.g. the raspberry Pi 3). When in AP mode an a
> scan is issued clients will disconnect. After testing this behavior
> was isolated to the use of the COLOCATED_6GHZ flag.
>
> Besides working around the problem on this specific hardware the
> patch itself makes sense as a non-6GHz capable device shouldn't use
> this flag anyways.
>
> As stated in the patch comment, this isn't really a catch all
> workaround since the flag is still used for devices supporting 6GHz.
> If additional hardware exhibits this behavior we may need additional
> changes like a hardware blacklist or an explicit option to disable
> the flag.
>
> Reported-By: Keith G <ys3al35l@gmail.com>

Could you double check it still fixes the issue you were seeing on brcmfmac?

Thanks,

James

> ---
> src/scan.c | 15 ++++++++++++++-
> 1 file changed, 14 insertions(+), 1 deletion(-)
>
> diff --git a/src/scan.c b/src/scan.c
> index f48ffdef..8c6fdc08 100644
> --- a/src/scan.c
> +++ b/src/scan.c
> @@ -394,7 +394,20 @@ static struct l_genl_msg *scan_build_cmd(struct scan_context *sc,
> if (params->ap_scan)
> flags |= NL80211_SCAN_FLAG_AP;
>
> - flags |= NL80211_SCAN_FLAG_COLOCATED_6GHZ;
> + /*
> + * TODO: This flag appears to cause some undesired behavior on brcmfmac
> + * when the device is in AP mode, or has a secondary AP interface
> + * running, causing clients to disconnect when a scan is issued.
> + *
> + * Only using this flag for 6GHz capable devices will limit this
> + * behavior to only 6GHz devices and in reality makes sense
> + * because a non-6GHz device shouldn't use this flag anyways. If
> + * more issues still are seen related to this we may need an
> + * explicit workaround, either brcmfmac-specific or a disable
> + * option.
> + */
> + if (wiphy_band_is_disabled(sc->wiphy, BAND_FREQ_6_GHZ) != -ENOTSUP)
> + flags |= NL80211_SCAN_FLAG_COLOCATED_6GHZ;
>
> if (flags)
> l_genl_msg_append_attr(msg, NL80211_ATTR_SCAN_FLAGS, 4, &flags);