Re: [PATCH] wifi: mt76: mt7921: avoid undesired changes of the preset regulatory domain

["Mingyen Hsieh (謝明諺)" <Mingyen.Hsieh@mediatek.com>]

On Mon, 2025-01-06 at 05:50 +0000, Mingyen Hsieh (謝明諺) wrote:
> 
> 
> -----Original Message-----
> From: Felix Fietkau <nbd@nbd.name> 
> Sent: Tuesday, December 31, 2024 3:05 AM
> To: Mingyen Hsieh (謝明諺) <Mingyen.Hsieh@mediatek.com>;
> lorenzo@kernel.org
> Cc: Deren Wu (武德仁) <Deren.Wu@mediatek.com>; Sean Wang
> <Sean.Wang@mediatek.com>; Soul Huang (黃至昶) <Soul.Huang@mediatek.com>;
> Leon Yen (顏良儒) <Leon.Yen@mediatek.com>; Eric-SY Chang (張書源)
> <Eric-SY.Chang@mediatek.com>; KM Lin (林昆民) <km.lin@mediatek.com>;
> Robin Chiu (邱國濱) <robin.chiu@mediatek.com>; CH Yeh (葉志豪)
> <ch.yeh@mediatek.com>; Posh Sun (孫瑞廷) <posh.sun@mediatek.com>; Quan
> Zhou (周全) <Quan.Zhou@mediatek.com>; Ryder Lee
> <Ryder.Lee@mediatek.com>; Shayne Chen (陳軒丞)
> <Shayne.Chen@mediatek.com>; linux-wireless@vger.kernel.org;
> linux-mediatek@lists.infradead.org
> Subject: Re: [PATCH] wifi: mt76: mt7921: avoid undesired changes of
> the preset regulatory domain
> 
> 
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> 
> 
> On 12.04.24 10:53, Mingyen Hsieh wrote:
> > From: Leon Yen <leon.yen@mediatek.com>
> > 
> > Some countries have strict RF restrictions where changing the 
> > regulatory domain dynamically based on the connected AP is not
> > acceptable.
> > This patch disables Beacon country IE hinting when a valid country 
> > code is set from usersland (e.g., by system using iw or CRDA).
> > 
> > Signed-off-by: Leon Yen <leon.yen@mediatek.com>
> > Signed-off-by: Ming Yen Hsieh <mingyen.hsieh@mediatek.com>
> > ---
> >   drivers/net/wireless/mediatek/mt76/mt7921/init.c | 7 +++++++
> >   1 file changed, 7 insertions(+)
> > 
> > diff --git a/drivers/net/wireless/mediatek/mt76/mt7921/init.c 
> > b/drivers/net/wireless/mediatek/mt76/mt7921/init.c
> > index ef0c721d26e3..3c9a5fcd6924 100644
> > --- a/drivers/net/wireless/mediatek/mt76/mt7921/init.c
> > +++ b/drivers/net/wireless/mediatek/mt76/mt7921/init.c
> > @@ -135,6 +135,13 @@ mt7921_regd_notifier(struct wiphy *wiphy,
> >       dev->mt76.region = request->dfs_region;
> >       dev->country_ie_env = request->country_ie_env;
> > 
> > +     if (request->initiator == NL80211_REGDOM_SET_BY_USER) {
> > +             if (dev->mt76.alpha2[0] == '0' && dev->mt76.alpha2[1]
> > == '0')
> > +                     wiphy->regulatory_flags &=
> > ~REGULATORY_COUNTRY_IE_IGNORE;
> > +             else
> > +                     wiphy->regulatory_flags |=
> > REGULATORY_COUNTRY_IE_IGNORE;
> > +     }
> > +
> 
> Sorry for the late response, I just noticed that I completely forgot
> to review this one.
> 
> In principle, it makes sense to me to ignore the country IE in this
> case, however I don't understand why the change is done in the mt7921
> driver. Isn't this a generic issue that should be consistent across
> drivers and thus better handled in mac80211?
> 
> Thanks,
> 
> - Felix

Hi,

Thank you for the review.

The purpose of this patch is not to fix a bug;
instead, it changes how the driver treats the beacon country IE hint
and has both advantages and disadvantages. With this patch, the beacon
country IE hinting will be disabled on a country code preset system,
which might cause some issues during overseas travel in certain
situations. it's a trade-off, I believe it's better to allow the
developers of each wifi dirver to decide how to manage it and keeping
mac80211 flexible.

yen.