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Subject: Re: [RFC] Introduce NL80211_IFTYPE_MLO_LINK_DEVICE for MLO link (IEEE
 802.11be)
To:     Johannes Berg <johannes@sipsolutions.net>,
        Sunil Dutt <usdutt@codeaurora.org>
Cc:     linux-wireless@vger.kernel.org
References: <1607526302-8063-1-git-send-email-usdutt@codeaurora.org>
 <9320c4f30cd3ba67ababf8e245963b656e2bf1ad.camel@sipsolutions.net>
From:   Arend van Spriel <arend.vanspriel@broadcom.com>
Message-ID: <73cb65ef-8635-5aad-d22d-3764e919f55d@broadcom.com>
Date:   Mon, 14 Dec 2020 10:25:35 +0100
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On 09-12-2020 16:36, Johannes Berg wrote:
> Hi,
> 
>> Multi-link support is introduced in 802.11be specification.
> [...]
> 
> I'll definitely have to take a closer look at this and the spec and
> think about it - but a couple of quick comments below.

Did not get my hands on the spec yet, but just firing random thoughts. 
This multi-link support sounds a bit like bonding. Could that be 
leveraged for wireless? I wonder why there is a need for a non-netdev 
interface. Does networking layer need to be aware of the multi-link for 
scheduling traffic to it? Is there one driver per multi-link or per radio?

[...]

>>   	struct sk_buff *msg;
>>   	void *hdr;
>> +	struct nlattr *nested, *nested_mlo_links;
>> +	struct cfg80211_mlo_link_device_params *mlo_link;
>> +	int i = 0;
>>   
>>   	msg = nlmsg_new(100 + cr->req_ie_len + cr->resp_ie_len +
>>   			cr->fils.kek_len + cr->fils.pmk_len +
>> -			(cr->fils.pmkid ? WLAN_PMKID_LEN : 0), gfp);
>> +			(cr->fils.pmkid ? WLAN_PMKID_LEN : 0) +
>> +			(cr->n_mlo_links ? cr->n_mlo_links * 32 : 0), gfp);
> 
> 32 probably should be some NLA_SIZE or something constant?

Probably sizeof(*mlo_link) ?

> There's also no point in the ternary operator since 0 * 32 is 0 :)
> 
>>   /* Consumes bss object one way or another */
>> @@ -833,7 +849,9 @@ void cfg80211_connect_done(struct net_device *dev,
>>   	ev = kzalloc(sizeof(*ev) + (params->bssid ? ETH_ALEN : 0) +
>>   		     params->req_ie_len + params->resp_ie_len +
>>   		     params->fils.kek_len + params->fils.pmk_len +
>> -		     (params->fils.pmkid ? WLAN_PMKID_LEN : 0), gfp);
>> +		     (params->fils.pmkid ? WLAN_PMKID_LEN : 0) +
>> +		     (params->n_mlo_links ? params->n_mlo_links *
>> +		      sizeof(struct cfg80211_mlo_link_device_params) : 0), gfp);
> 
> same here, no need for the ternary
> 
> 
> It feels strangely asymmetric to have stop and no start ... but I guess
> that's the part where I need to think about it and look a bit at how it
> all works :)

Had the same feeling in my gutt (wherever that is ;-)

Regards,
Arend

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