linux-kernel - Re: [PATCH V7 4/9] wifi: mac80211: Add support for ACPI WBRF

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Date:   Mon, 24 Jul 2023 11:22:48 +0200
From:   Andrew Lunn <andrew@...n.ch>
To:     Evan Quan <evan.quan@....com>
Cc:     rafael@...nel.org, lenb@...nel.org, Alexander.Deucher@....com,
        Christian.Koenig@....com, Xinhui.Pan@....com, airlied@...il.com,
        daniel@...ll.ch, johannes@...solutions.net, davem@...emloft.net,
        edumazet@...gle.com, kuba@...nel.org, pabeni@...hat.com,
        Mario.Limonciello@....com, mdaenzer@...hat.com,
        maarten.lankhorst@...ux.intel.com, tzimmermann@...e.de,
        hdegoede@...hat.com, jingyuwang_vip@....com, Lijo.Lazar@....com,
        jim.cromie@...il.com, bellosilicio@...il.com,
        andrealmeid@...lia.com, trix@...hat.com, jsg@....id.au,
        arnd@...db.de, linux-kernel@...r.kernel.org,
        linux-acpi@...r.kernel.org, amd-gfx@...ts.freedesktop.org,
        dri-devel@...ts.freedesktop.org, linux-wireless@...r.kernel.org,
        netdev@...r.kernel.org
Subject: Re: [PATCH V7 4/9] wifi: mac80211: Add support for ACPI WBRF

> @@ -1395,6 +1395,8 @@ int ieee80211_register_hw(struct ieee80211_hw *hw)
>  	debugfs_hw_add(local);
>  	rate_control_add_debugfs(local);
>  
> +	ieee80211_check_wbrf_support(local);
> +
>  	rtnl_lock();
>  	wiphy_lock(hw->wiphy);
>  

> +void ieee80211_check_wbrf_support(struct ieee80211_local *local)
> +{
> +	struct wiphy *wiphy = local->hw.wiphy;
> +	struct device *dev;
> +
> +	if (!wiphy)
> +		return;
> +
> +	dev = wiphy->dev.parent;
> +	if (!dev)
> +		return;
> +
> +	local->wbrf_supported = wbrf_supported_producer(dev);
> +	dev_dbg(dev, "WBRF is %s supported\n",
> +		local->wbrf_supported ? "" : "not");
> +}

This seems wrong. wbrf_supported_producer() is about "Should this
device report the frequencies it is using?" The answer to that depends
on a combination of: Are there consumers registered with the core, and
is the policy set so WBRF should take actions.

The problem here is, you have no idea of the probe order. It could be
this device probes before others, so wbrf_supported_producer() reports
false, but a few second later would report true, once other devices
have probed.

It should be an inexpensive call into the core, so can be made every
time the channel changes. All the core needs to do is check if the
list of consumers is empty, and if not, check a Boolean policy value.

     Andrew