Re: [PATCH wireless-next v2 0/5] wifi: cfg80211: Add support to indicate changed AP BSS parameters to drivers

On 06/03, Johannes Berg wrote:
> On Tue, 2025-06-03 at 16:02 +0530, Gokul Sivakumar wrote:
> > In cfg80211, added provision for the drivers which registers the callback
> > .change_bss() cfg80211_ops, to find which set of AP BSS params are changed
> > by the userpsace in the SET_BSS operation. With this the drivers can decide
> > to reject the operation if any of the changed AP BSS param is not supported
> > for explicit configuration. This helps ensuring that the driver does not
> > partially handle the AP BSS params and avoid misleading the userspace that
> > the SET_BSS operation is fully successful.
> >
> > Also introduced the "changed" bitmask check in all the drivers that are
> > currently registering to .change_bss() cfg80211_ops. This would make the
> > condition for handling SET_BSS operation equally stirct across all drivers.
> >
> 
> Oh, nice! I'll have to look at it in more detail later, but one thing I
> saw now is in patch 2 you have this:
> 
> > In AP mode, the "ap_isolate" value from the cfg80211 layer represents,
> >  0 = allow low-level bridging of frames between associated stations
> >  1 = restrict low-level bridging of frames to isolate associated stations
> > -1 = do not change existing setting
> 
> Is that -1 still true? Seems like now it should just be that
> CFG80211_BSS_PARAM_CHANGED_AP_ISOLATE isn't set and then you don't touch
> it?
> 

Apologies for the HTML content in my earlier reply which got rejected by
the mailing list.

Kindly note that the driver is rejecting the SET_BSS operation if an
unsupported AP BSS param is passed by userspace, while the opposite is not
true. ie. the operation would not be rejected by the driver, when a
supported AP BSS param is not passed by the userspace.

So yes, the significance of "-1" still holds true, because if suppose the
userspace skipped this param in the SET_BSS request, the driver when
receiving the request will have the ap_isolate param with the default
value "-1". The driver is checking if the param value is >=0 before
proceeding with handling it. And will ignore the param, only if it is -1.

Gokul