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Sender: Larry Finger <larry.finger@gmail.com>
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Date:   Tue, 16 May 2023 12:53:03 -0500
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Subject: Re: [PATCH] wifi: b43: fix incorrect __packed annotation
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To:     Arnd Bergmann <arnd@kernel.org>, Kalle Valo <kvalo@kernel.org>
Cc:     Arnd Bergmann <arnd@arndb.de>,
        "David S. Miller" <davem@davemloft.net>,
        Eric Dumazet <edumazet@google.com>,
        Jakub Kicinski <kuba@kernel.org>,
        Paolo Abeni <pabeni@redhat.com>,
        Nathan Chancellor <nathan@kernel.org>,
        Nick Desaulniers <ndesaulniers@google.com>,
        Tom Rix <trix@redhat.com>, linux-wireless@vger.kernel.org,
        b43-dev@lists.infradead.org, netdev@vger.kernel.org,
        linux-kernel@vger.kernel.org, llvm@lists.linux.dev
References: <20230516074554.1674536-1-arnd@kernel.org>
From:   Larry Finger <Larry.Finger@lwfinger.net>
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On 5/16/23 02:45, Arnd Bergmann wrote:
> From: Arnd Bergmann <arnd@arndb.de>
> 
> clang warns about an unpacked structure inside of a packed one:
> 
> drivers/net/wireless/broadcom/b43/b43.h:654:4: error: field data within 'struct b43_iv' is less aligned than 'union (unnamed union at /home/arnd/arm-soc/drivers/net/wireless/broadcom/b43/b43.h:651:2)' and is usually due to 'struct b43_iv' being packed, which can lead to unaligned accesses [-Werror,-Wunaligned-access]
> 
> The problem here is that the anonymous union has the default alignment
> from its members, apparently because the original author mixed up the
> placement of the __packed attribute by placing it next to the struct
> member rather than the union definition. As the struct itself is
> also marked as __packed, there is no need to mark its members, so just
> move the annotation to the inner type instead.
> 
> Signed-off-by: Arnd Bergmann <arnd@arndb.de>
> ---
>   drivers/net/wireless/broadcom/b43/b43.h | 2 +-
>   1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/drivers/net/wireless/broadcom/b43/b43.h b/drivers/net/wireless/broadcom/b43/b43.h
> index 9fc7c088a539..67b4bac048e5 100644
> --- a/drivers/net/wireless/broadcom/b43/b43.h
> +++ b/drivers/net/wireless/broadcom/b43/b43.h
> @@ -651,7 +651,7 @@ struct b43_iv {
>   	union {
>   		__be16 d16;
>   		__be32 d32;
> -	} data __packed;
> +	} __packed data >   } __packed;

This change works on a BCM4306 and BCM4318=.

Tested-by: Larry Finger <Larry.Finger@lwfinger.net>

To answer Michael's question, b43legacy has the same issue.

Larry


Larry