netdev - Re: [PATCH] carl9170: fix struct alignment conflict

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Date:   Tue,  9 Feb 2021 07:24:36 +0000 (UTC)
From:   Kalle Valo <kvalo@...eaurora.org>
To:     Arnd Bergmann <arnd@...nel.org>
Cc:     Christian Lamparter <chunkeey@...glemail.com>,
        "David S. Miller" <davem@...emloft.net>,
        Jakub Kicinski <kuba@...nel.org>,
        Arnd Bergmann <arnd@...db.de>,
        "Gustavo A. R. Silva" <gustavoars@...nel.org>,
        linux-wireless@...r.kernel.org, netdev@...r.kernel.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH] carl9170: fix struct alignment conflict

Arnd Bergmann <arnd@...nel.org> wrote:

> Multiple structures in the carl9170 driver have alignment
> impossible alignment constraints that gcc warns about when
> building with 'make W=1':
> 
> drivers/net/wireless/ath/carl9170/fwcmd.h:243:2: warning: alignment 1 of 'union <anonymous>' is less than 4 [-Wpacked-not-aligned]
> drivers/net/wireless/ath/carl9170/wlan.h:373:1: warning: alignment 1 of 'struct ar9170_rx_frame_single' is less than 2 [-Wpacked-not-aligned]
> 
> In the carl9170_cmd structure, multiple members that have an explicit
> alignment requirement of four bytes are added into a union with explicit
> byte alignment, but this in turn is part of a structure that also has
> four-byte alignment.
> 
> In the wlan.h header, multiple structures contain a ieee80211_hdr member
> that is required to be two-byte aligned to avoid alignmnet faults when
> processing network headers, but all members are forced to be byte-aligned
> using the __packed tag at the end of the struct definition.
> 
> In both cases, leaving out the packing does not change the internal
> layout of the structure but changes the alignment constraint of the
> structure itself.
> 
> Change all affected structures to only apply packing where it does
> not violate the alignment requirement of the contained structure.
> 
> Signed-off-by: Arnd Bergmann <arnd@...db.de>
> Acked-by: Christian Lamparter <chunkeey@...il.com>
> Signed-off-by: Kalle Valo <kvalo@...eaurora.org>

Patch applied to ath-next branch of ath.git, thanks.

ca9ad549e404 carl9170: fix struct alignment conflict

-- 
https://patchwork.kernel.org/project/linux-wireless/patch/20210204162926.3262598-1-arnd@kernel.org/

https://wireless.wiki.kernel.org/en/developers/documentation/submittingpatches