Re: [RFC v3 3/8] wifi: cfg80211: extend interface combination check for multi-radio

[Johannes Berg <johannes@sipsolutions.net>]

On Thu, 2024-06-06 at 20:07 +0200, Felix Fietkau wrote:
> 
> @@ -4577,6 +4579,7 @@ struct mgmt_frame_regs {
>   *
>   * @set_hw_timestamp: Enable/disable HW timestamping of TM/FTM frames.
>   * @set_ttlm: set the TID to link mapping.
> + * @get_radio_mask: get bitmask of radios in use
>   */
>  struct cfg80211_ops {
>  	int	(*suspend)(struct wiphy *wiphy, struct cfg80211_wowlan *wow);
> @@ -4938,6 +4941,8 @@ struct cfg80211_ops {
>  				    struct cfg80211_set_hw_timestamp *hwts);
>  	int	(*set_ttlm)(struct wiphy *wiphy, struct net_device *dev,
>  			    struct cfg80211_ttlm_params *params);
> +	int	(*get_radio_mask)(struct wiphy *wiphy, struct net_device *dev,
> +				  u32 *mask);


not sure I see the point of this being a callback rather than being
passed in?

(Also, if really needed, do you actually expect a device with 32 radios?
if not you can use a return value instead of u32 *mask out pointer :) )


> +DEFINE_EVENT(wiphy_netdev_evt, rdev_get_radio_mask,
> +	TP_PROTO(struct wiphy *wiphy, struct net_device *netdev),
> +	TP_ARGS(wiphy, netdev)
> +);

and if we do need it that really should trace not just the fact that it
happened but also the return value and mask

>  static void cfg80211_calculate_bi_data(struct wiphy *wiphy, u32 new_beacon_int,
>  				       u32 *beacon_int_gcd,
> -				       bool *beacon_int_different)
> +				       bool *beacon_int_different,
> +				       const struct wiphy_radio *radio)
>  {
> +	struct cfg80211_registered_device *rdev;
>  	struct wireless_dev *wdev;
> +	int radio_idx = -1;
>  
>  	*beacon_int_gcd = 0;
>  	*beacon_int_different = false;
> +	if (radio)
> +		radio_idx = radio - wiphy->radio;

This can go oh so wrong ... and technically even be UB. I'd rather pass
the index from the driver, I guess, and validate it against n_radios.
 
> +	rdev = wiphy_to_rdev(wiphy);
>  	list_for_each_entry(wdev, &wiphy->wdev_list, list) {
>  		int wdev_bi;
> +		u32 mask;
>  
>  		/* this feature isn't supported with MLO */
>  		if (wdev->valid_links)
>  			continue;

Are we expecting this to change? because the premise of this patchset is
MLO support, and yet with real MLO we won't get here?

Or is that because non-MLO interfaces could be created on this wiphy?

>  
> +		if (radio_idx >= 0) {
> +			if (rdev_get_radio_mask(rdev, wdev->netdev, &mask))
> +				continue;


here: given that 'radio'/'radio_idx' is passed in, not sure I see why
the mask couldn't also be passed in?

> +			if (!(mask & BIT(radio_idx)))
> +				continue;

that could use a comment

> -	for (i = 0; i < wiphy->n_iface_combinations; i++) {
> -		const struct ieee80211_iface_combination *c;
> +	if (radio) {
> +		c = radio->iface_combinations;
> +		n = radio->n_iface_combinations;
> +	} else {
> +		c = wiphy->iface_combinations;
> +		n = wiphy->n_iface_combinations;
> +	}
> +	for (i = 0; i < n; i++, c++) {

that c++ is a bit too hidden for my taste there, but YMMV and I guess if
I wasn't reading the diff it'd be more obvious :)

johannes