Re: [PATCH][next] wifi: mt76: mt7921: Replace fake flex-arrays with flexible-array members

From: Simon Horman <simon.horman@corigine.com>
To: "Gustavo A. R. Silva" <gustavoars@kernel.org>
Cc: Felix Fietkau <nbd@nbd.name>,
	Lorenzo Bianconi <lorenzo@kernel.org>,
	Ryder Lee <ryder.lee@mediatek.com>,
	Shayne Chen <shayne.chen@mediatek.com>,
	Sean Wang <sean.wang@mediatek.com>, Kalle Valo <kvalo@kernel.org>,
	"David S. Miller" <davem@davemloft.net>,
	Eric Dumazet <edumazet@google.com>,
	Jakub Kicinski <kuba@kernel.org>, Paolo Abeni <pabeni@redhat.com>,
	Matthias Brugger <matthias.bgg@gmail.com>,
	AngeloGioacchino Del Regno 
	<angelogioacchino.delregno@collabora.com>,
	linux-wireless@vger.kernel.org, netdev@vger.kernel.org,
	linux-kernel@vger.kernel.org,
	linux-arm-kernel@lists.infradead.org,
	linux-mediatek@lists.infradead.org,
	linux-hardening@vger.kernel.org
Subject: Re: [PATCH][next] wifi: mt76: mt7921: Replace fake flex-arrays with flexible-array members
Date: Mon, 20 Mar 2023 20:48:22 +0100	[thread overview]
Message-ID: <ZBi4hv5Q6lp2ooSV@corigine.com> (raw)
In-Reply-To: <ZBizeZ5DaBT5KKXN@work>

On Mon, Mar 20, 2023 at 01:26:49PM -0600, Gustavo A. R. Silva wrote:
> On Mon, Mar 20, 2023 at 03:56:54PM +0100, Simon Horman wrote:
> > >  struct mt7921_asar_cl {
> > > @@ -85,7 +85,7 @@ struct mt7921_asar_fg {
> > >  	u8 rsvd;
> > >  	u8 nr_flag;
> > >  	u8 rsvd1;
> > > -	u8 flag[0];
> > > +	u8 flag[];
> > 
> > I am curious to know why DECLARE_FLEX_ARRAY isn't used here.
> 
> In contrast to the other structs, there is no object of type struct
> mt7921_asar_fg declared in a union:
> 
>  91 struct mt7921_acpi_sar {
>  92         u8 ver;
>  93         union {
>  94                 struct mt7921_asar_dyn *dyn;
>  95                 struct mt7921_asar_dyn_v2 *dyn_v2;
>  96         };
>  97         union {
>  98                 struct mt7921_asar_geo *geo;
>  99                 struct mt7921_asar_geo_v2 *geo_v2;
> 100         };
> 101         struct mt7921_asar_cl *countrylist;
> 102         struct mt7921_asar_fg *fg;
> 103 };
> 
> The DECLARE_FLEX_ARRAY() helper was created to declare flex-array members
> in unions or alone in structs[1].

Thanks for the clarification, much appreciated.

FWIIW, with this information I'm happy with this patch.

Reviewed-by: Simon Horman <simon.horman@corigine.com>