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To:     Luca Coelho <luca@coelho.fi>, johannes@sipsolutions.net
Cc:     linux-wireless@vger.kernel.org
References: <20201129153055.1971298-1-luca@coelho.fi>
 <iwlwifi.20201129172929.290fa5c5568a.Ic5732aa64de6ee97ae3578bd5779fc723ba489d1@changeid>
From:   Nicolas Cavallari <Nicolas.Cavallari@green-communications.fr>
Subject: Re: [PATCH 09/13] cfg80211: Save the regulatory domain when setting
 custom regulatory
Message-ID: <e8e6afa6-275e-2cc5-6351-e1ed5eb0e0af@green-communications.fr>
Date:   Tue, 15 Jun 2021 16:42:20 +0200
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On 29/11/2020 16:30, Luca Coelho wrote:
> From: Ilan Peer <ilan.peer@intel.com>
> 
> When custom regulatory was set, only the channels setting was updated, but
> the regulatory domain was not saved. Fix it by saving it.
> 
> Signed-off-by: Ilan Peer <ilan.peer@intel.com>
> Signed-off-by: Luca Coelho <luciano.coelho@intel.com>
> ---
>   net/wireless/reg.c | 8 ++++++++
>   1 file changed, 8 insertions(+)
> 
> diff --git a/net/wireless/reg.c b/net/wireless/reg.c
> index a04fdfb35f07..094492b62f8a 100644
> --- a/net/wireless/reg.c
> +++ b/net/wireless/reg.c
> @@ -2547,6 +2547,7 @@ static void handle_band_custom(struct wiphy *wiphy,
>   void wiphy_apply_custom_regulatory(struct wiphy *wiphy,
>   				   const struct ieee80211_regdomain *regd)
>   {
> +	const struct ieee80211_regdomain *new_regd, *tmp;
>   	enum nl80211_band band;
>   	unsigned int bands_set = 0;
>   
> @@ -2566,6 +2567,13 @@ void wiphy_apply_custom_regulatory(struct wiphy *wiphy,
>   	 * on your device's supported bands.
>   	 */
>   	WARN_ON(!bands_set);
> +	new_regd = reg_copy_regd(regd);
> +	if (IS_ERR(new_regd))
> +		return;
> +
> +	tmp = get_wiphy_regdom(wiphy);
> +	rcu_assign_pointer(wiphy->regd, new_regd);
> +	rcu_free_regdom(tmp);
>   }
>   EXPORT_SYMBOL(wiphy_apply_custom_regulatory);
>   
> 

Hello,

This patch somehow appears to break ath9k's eeprom hints and restrict it to the 
world regulatory domain on v5.12.10.

ath9k calls wiphy_apply_custom_regulatory() with its own kind of world 
regulatory domain, before it decodes hints from the eeprom and uses 
regulatory_hint() to request a specific alpha2.

With this patch, applying the hint fails because wiphy->regd is already set.
If i revert this patch, ath9k works again.