Re: [RFC 1/4] wifi: cfg80211: Add provision to advertise multiple radio in one wiphy

[Vasanthakumar Thiagarajan <quic_vthiagar@quicinc.com>]

On 10/21/2022 5:34 PM, Johannes Berg wrote:
> On Tue, 2022-09-20 at 15:35 +0530, Vasanthakumar Thiagarajan wrote:
>> The prerequisite for MLO support in cfg80211/mac80211 is that all
>> the links participating in MLO must be from the same wiphy/ieee80211_hw.
>> To meet this expectation, some drivers may need to group multiple discrete
>> hardware each acting as a link in MLO under one wiphy. Though most of the
>> hardware abstractions must be handled within the driver itself, it may be
>> required to have some sort of mapping while describing interface
>> combination capabilities for each of the underlying hardware. This commit
>> adds an advertisement provision for drivers supporting such MLO mode of
>> operation.
>>
>> Capability advertisement such as the number of supported channels for each
>> physical hardware has been identified to support some of the common use
>> cases.
>>
>> Signed-off-by: Vasanthakumar Thiagarajan <quic_vthiagar@quicinc.com>
>> ---
>>   include/net/cfg80211.h |  24 +++++++++
>>   net/wireless/core.c    | 109 +++++++++++++++++++++++++++++++++++++++++
>>   2 files changed, 133 insertions(+)
>>
>> diff --git a/include/net/cfg80211.h b/include/net/cfg80211.h
>> index e09ff87146c1..4662231ad068 100644
>> --- a/include/net/cfg80211.h
>> +++ b/include/net/cfg80211.h
>> @@ -5088,6 +5088,18 @@ struct wiphy_iftype_akm_suites {
>>   	int n_akm_suites;
>>   };
>>   
>> +/**
>> + * struct ieee80211_supported_chans_per_hw - supported channels as per the
>> + * underlying physical hardware configuration
>> + *
>> + * @n_chans: number of channels in @chans
>> + * @chans: list of channels supported by the constituent hardware
>> + */
>> +struct ieee80211_chans_per_hw {
>> +	int n_chans;
> 
> nit: unsigned?
> 
>> + * @hw_chans: list of the channels supported by every constituent underlying
> 
> "every" here refers to the fact that you have all the channels, right? I
> mean, hw_chans is per hardware, basically.

Correct, it refers all the channels supported per hardware registered 
something like below

hw_chans[0] =	{
  			// 2 GHz radio
			<num_2ghz_chans>,
			{
				<ieee80211_channel_2ghz_1>,
				<ieee80211_channel_2ghz_2>, ...
			}
		}

hw_chans[1] = {
		{
  			// 5 GHz radio
			<num_5ghz_chans>,
			{
				<ieee80211_channel_5ghz_1>,
				<ieee80211_channel_5ghz_2>, ...
			}
		}
		
...


> 
>> + *	hardware. Drivers abstracting multiple discrete hardware (radio) under
>> + *	one wiphy can advertise the list of channels supported by each physical
>> + *	hardware in this list. Underlying hardware specific channel list can be
>> + *	used while describing interface combination for each of them.
>> + * @num_hw: number of underlying hardware for which the channels list are
>> + *	advertised in @hw_chans.
>> + *
>>    */
>>   struct wiphy {
>>   	struct mutex mtx;
>> @@ -5445,6 +5466,9 @@ struct wiphy {
>>   	u8 ema_max_profile_periodicity;
>>   	u16 max_num_akm_suites;
>>   
>> +	struct ieee80211_chans_per_hw **hw_chans;
>> +	int num_hw;
> 
> also here, maybe unsigned.
> 
>> +static bool
>> +cfg80211_hw_chans_in_supported_list(struct wiphy *wiphy,
>> +				    const struct ieee80211_chans_per_hw *chans)
>> +{
>> +	enum nl80211_band band;
>> +	struct ieee80211_supported_band *sband;
>> +	bool found;
>> +	int i, j;
>> +
>> +	for (i = 0; i < chans->n_chans; i++) {
>> +		found = false;
> 
> nit: you can move the variable declaration here
> 
> 	bool found = false;
> 	\n
> 
> since you don't need it outside the loop.
> 
>> +	for (i = 0; i < wiphy->num_hw; i++) {
>> +		for (j = 0; j < wiphy->num_hw; j++) {
>> +			const struct ieee80211_chans_per_hw *hw_chans1;
>> +			const struct ieee80211_chans_per_hw *hw_chans2;
>> +
>> +			if (i == j)
>> +				continue;
> 
> It's symmetric, if I read the code above right, so you can do
> 
> 	for (j = i; j < ...; j++)
> 
> in the second loop and avoid this?

Sure

> 
> 
>> +		hw_chans = wiphy->hw_chans[i];
>> +		if (!cfg80211_hw_chans_in_supported_list(wiphy, hw_chans)) {
>> +			WARN_ON(1);
> 
> I can kind of see the point in not using WARN_ON(!cfg80211_hw_chans...)
> since it gets really long, but maybe just remove the warning?
>   
>> +	if (cfg80211_validate_per_hw_chans(&rdev->wiphy)) {
>> +		WARN_ON(1);
>> +		return -EINVAL;
>>
> 
> Anyway you'll have one here, and it's not directly visible which
> condition failed anyway.
> 
> And you could use WARN_ON(validate(...)) here :)

Sure, thanks!

Vasanth