linux-kernel - Re: [PATCH v2] brcmfmac: add support for CQM RSSI notifications

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Date:   Fri, 15 Jan 2021 16:08:02 +0100
From:   Arend van Spriel <arend.vanspriel@...adcom.com>
To:     Andrew Zaborowski <andrew.zaborowski@...el.com>
Cc:     Alvin Šipraga <ALSI@...g-olufsen.dk>,
        Arend van Spriel <aspriel@...il.com>,
        Franky Lin <franky.lin@...adcom.com>,
        Hante Meuleman <hante.meuleman@...adcom.com>,
        Chi-hsien Lin <chi-hsien.lin@...ineon.com>,
        Wright Feng <wright.feng@...ineon.com>,
        Chung-hsien Hsu <chung-hsien.hsu@...ineon.com>,
        Kalle Valo <kvalo@...eaurora.org>,
        "linux-wireless@...r.kernel.org" <linux-wireless@...r.kernel.org>,
        "brcm80211-dev-list.pdl@...adcom.com" 
        <brcm80211-dev-list.pdl@...adcom.com>,
        "SHA-cyfmac-dev-list@...ineon.com" <SHA-cyfmac-dev-list@...ineon.com>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH v2] brcmfmac: add support for CQM RSSI notifications

On 1/15/2021 3:51 PM, Andrew Zaborowski wrote:
> On Fri, 15 Jan 2021 at 15:12, Arend Van Spriel
> <arend.vanspriel@...adcom.com> wrote:>
>> + Johannes
>> - netdevs
>>
>> On 1/14/2021 5:36 PM, 'Alvin Šipraga' via BRCM80211-DEV-LIST,PDL wrote:
>>> Add support for CQM RSSI measurement reporting and advertise the
>>> NL80211_EXT_FEATURE_CQM_RSSI_LIST feature. This enables a userspace
>>> supplicant such as iwd to be notified of changes in the RSSI for roaming
>>> and signal monitoring purposes.
>>
>> The more I am looking into this API the less I understand it or at least
>> it raises a couple of questions. Looking into nl80211_set_cqm_rssi() [1]
>> two behaviors are supported: 1) driver is provisioned with a threshold
>> and hysteresis, or 2) driver is provisioned with high and low threshold.
> 
> Right.
> 
>>
>> The second behavior is used when the driver advertises
>> NL80211_EXT_FEATURE_CQM_RSSI_LIST *and* user-space provides more than
>> one RSSI threshold.
> 
> Or, when the driver doesn't implement set_cqm_rssi_config (the old
> method).  So the driver can stop supporting set_cqm_rssi_config when
> it implements set_cqm_rssi_range_config.

Argh. Totally overlooked these were two different callbacks. In that 
case it is easy to determine what is being requested.

Thanks,
Arend