linux-kernel - Re: [PATCH] mwifiex: Remove unnecessary braces from HostCmd_SET_SEQ_NO_BSS

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Date:   Tue, 1 Sep 2020 10:47:12 -0700
From:   Nick Desaulniers <ndesaulniers@...gle.com>
To:     Nathan Chancellor <natechancellor@...il.com>
Cc:     Amitkumar Karwar <amitkarwar@...il.com>,
        Ganapathi Bhat <ganapathi.bhat@....com>,
        Xinming Hu <huxinming820@...il.com>,
        Kalle Valo <kvalo@...eaurora.org>,
        linux-wireless <linux-wireless@...r.kernel.org>,
        Network Development <netdev@...r.kernel.org>,
        LKML <linux-kernel@...r.kernel.org>,
        clang-built-linux <clang-built-linux@...glegroups.com>,
        Andy Lavr <andy.lavr@...il.com>
Subject: Re: [PATCH] mwifiex: Remove unnecessary braces from HostCmd_SET_SEQ_NO_BSS_INFO

On Tue, Sep 1, 2020 at 12:08 AM Nathan Chancellor
<natechancellor@...il.com> wrote:
>
> A new warning in clang points out when macro expansion might result in a
> GNU C statement expression. There is an instance of this in the mwifiex
> driver:
>
> drivers/net/wireless/marvell/mwifiex/cmdevt.c:217:34: warning: '}' and
> ')' tokens terminating statement expression appear in different macro
> expansion contexts [-Wcompound-token-split-by-macro]
>         host_cmd->seq_num = cpu_to_le16(HostCmd_SET_SEQ_NO_BSS_INFO
>                                         ^~~~~~~~~~~~~~~~~~~~~~~~~~~
> drivers/net/wireless/marvell/mwifiex/fw.h:519:46: note: expanded from
> macro 'HostCmd_SET_SEQ_NO_BSS_INFO'
>         (((type) & 0x000f) << 12);                  }
>                                                     ^
>
> This does not appear to be a real issue. Removing the braces and
> replacing them with parentheses will fix the warning and not change the
> meaning of the code.
>
> Fixes: 5e6e3a92b9a4 ("wireless: mwifiex: initial commit for Marvell mwifiex driver")
> Link: https://github.com/ClangBuiltLinux/linux/issues/1146
> Reported-by: Andy Lavr <andy.lavr@...il.com>
> Signed-off-by: Nathan Chancellor <natechancellor@...il.com>

Wow, that's tricky. The unnecessary extra parens mix with the extra
curly braces to form a GNU C statement expression.  Thanks for the
patch.
Reviewed-by: Nick Desaulniers <ndesaulniers@...gle.com>

> ---
>  drivers/net/wireless/marvell/mwifiex/cmdevt.c | 4 ++--
>  drivers/net/wireless/marvell/mwifiex/fw.h     | 8 ++++----
>  2 files changed, 6 insertions(+), 6 deletions(-)
>
> diff --git a/drivers/net/wireless/marvell/mwifiex/cmdevt.c b/drivers/net/wireless/marvell/mwifiex/cmdevt.c
> index d068b9075c32..3a11342a6bde 100644
> --- a/drivers/net/wireless/marvell/mwifiex/cmdevt.c
> +++ b/drivers/net/wireless/marvell/mwifiex/cmdevt.c
> @@ -322,9 +322,9 @@ static int mwifiex_dnld_sleep_confirm_cmd(struct mwifiex_adapter *adapter)
>
>         adapter->seq_num++;
>         sleep_cfm_buf->seq_num =
> -               cpu_to_le16((HostCmd_SET_SEQ_NO_BSS_INFO
> +               cpu_to_le16(HostCmd_SET_SEQ_NO_BSS_INFO
>                                         (adapter->seq_num, priv->bss_num,
> -                                        priv->bss_type)));
> +                                        priv->bss_type));
>
>         mwifiex_dbg(adapter, CMD,
>                     "cmd: DNLD_CMD: %#x, act %#x, len %d, seqno %#x\n",
> diff --git a/drivers/net/wireless/marvell/mwifiex/fw.h b/drivers/net/wireless/marvell/mwifiex/fw.h
> index 8047e307892e..1f02c5058aed 100644
> --- a/drivers/net/wireless/marvell/mwifiex/fw.h
> +++ b/drivers/net/wireless/marvell/mwifiex/fw.h
> @@ -513,10 +513,10 @@ enum mwifiex_channel_flags {
>
>  #define RF_ANTENNA_AUTO                 0xFFFF
>
> -#define HostCmd_SET_SEQ_NO_BSS_INFO(seq, num, type) {   \
> -       (((seq) & 0x00ff) |                             \
> -        (((num) & 0x000f) << 8)) |                     \
> -       (((type) & 0x000f) << 12);                  }
> +#define HostCmd_SET_SEQ_NO_BSS_INFO(seq, num, type) \
> +       ((((seq) & 0x00ff) |                        \
> +        (((num) & 0x000f) << 8)) |                 \
> +       (((type) & 0x000f) << 12))
>
>  #define HostCmd_GET_SEQ_NO(seq)       \
>         ((seq) & HostCmd_SEQ_NUM_MASK)
> --

-- 
Thanks,
~Nick Desaulniers