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

[Felix Fietkau <nbd@nbd.name>]

On 07.06.24 11:32, Johannes Berg wrote:
> 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 :) )

I'll update the callback to return u32

>> +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.

Will pass the index in directly.

>> +	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?

Not sure about this. I guess we can revisit it later since it's out of 
scope for this series.

>>  
>> +		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?

mask is supposed to be per wdev, which is iterated in a loop here.

> 
>> +			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 :)

Will move it into the loop body to make it more obvious.

Thanks,

- Felix