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Date: Thu, 25 Jan 2024 10:32:53 -0800
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Subject: Re: [PATCH wireless v2] nl80211/cfg80211: add nla_policy for S1G band
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From: Jeff Johnson <quic_jjohnson@quicinc.com>
To: Johannes Berg <johannes@sipsolutions.net>, Lin Ma <linma@zju.edu.cn>,
        <davem@davemloft.net>, <edumazet@google.com>, <kuba@kernel.org>,
        <pabeni@redhat.com>, <linux-wireless@vger.kernel.org>,
        <netdev@vger.kernel.org>, <linux-kernel@vger.kernel.org>,
        <kvalo@kernel.org>
References: <20240119151201.8670-1-linma@zju.edu.cn>
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 <590fe2823d934af997c515640733eb8889b0560f.camel@sipsolutions.net>
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On 1/22/2024 10:33 AM, Jeff Johnson wrote:
> On 1/20/2024 12:27 PM, Johannes Berg wrote:
>> On Fri, 2024-01-19 at 15:47 -0800, Jeff Johnson wrote:
>>>> --- a/net/wireless/nl80211.c
>>>> +++ b/net/wireless/nl80211.c
>>>> @@ -911,6 +911,7 @@ nl80211_match_band_rssi_policy[NUM_NL80211_BANDS] = {
>>>>  	[NL80211_BAND_5GHZ] = { .type = NLA_S32 },
>>>>  	[NL80211_BAND_6GHZ] = { .type = NLA_S32 },
>>>>  	[NL80211_BAND_60GHZ] = { .type = NLA_S32 },
>>>> +	[NL80211_BAND_S1GHZ] = { .type = NLA_S32 },
>>>>  	[NL80211_BAND_LC]    = { .type = NLA_S32 },
>>>>  };
>>>>  
>>> something is really suspicious since the NL80211_BAND_* enums are
>>> *value* enums, not attribute ID enums, and hence they should never be
>>> used in an nla_policy.
>>
>> Yeah, that's what it looks like first, but then they do get used
>> anyway...
>>
>>> what is actually using these as attribute IDs, noting that
>>> NL80211_BAND_2GHZ == 0 and hence cannot be used as an attribute ID
>>
>> Ohh. Good catch!
>>
>>> seems the logic that introduced this policy needs to be revisited.
>>>
>>
>> Let's just remove it?
>>
>> commit 1e1b11b6a1111cd9e8af1fd6ccda270a9fa3eacf
>> Author: vamsi krishna <vamsin@codeaurora.org>
>> Date:   Fri Feb 1 18:34:51 2019 +0530
>>
>>     nl80211/cfg80211: Specify band specific min RSSI thresholds with sched scan
>>
>>
>> As far as I can tell nothing is using that in the first place ...
>> Certainly not in the kernel, nor wpa_s, nor anything else I could find
>> really ...
>>
>> We can't completely revert it since we need the attribute number to stay
>> allocated, but that's all we cannot remove.
> 
> I'm investigating this and will report back.

OK, I have investigated this and based upon the investigation this can
be removed (except for keeping the now obsolete uapi bits). This was
done in preparation for supporting a new Android interface in the
out-of-tree Android driver, but that interface was subsequently
withdrawn by Google.

Johannes, do you want to handle this? Or should I?

/jeff