linux-kernel - Re: [PATCH] wifi: ray_cs: Replace the ternary conditional operator with min()

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Message-ID: <ZJmEg5Jw4e9KZVfA@corigine.com>
Date:   Mon, 26 Jun 2023 14:28:51 +0200
From:   Simon Horman <simon.horman@...igine.com>
To:     You Kangren <youkangren@...o.com>
Cc:     Kalle Valo <kvalo@...nel.org>, Dongliang Mu <dzm91@...t.edu.cn>,
        Christophe JAILLET <christophe.jaillet@...adoo.fr>,
        "open list:RAYLINK/WEBGEAR 802.11 WIRELESS LAN DRIVER" 
        <linux-wireless@...r.kernel.org>,
        open list <linux-kernel@...r.kernel.org>,
        opensource.kernel@...o.com
Subject: Re: [PATCH] wifi: ray_cs: Replace the ternary conditional operator
 with min()

On Mon, Jun 26, 2023 at 05:35:02PM +0800, You Kangren wrote:
> Replace the ternary conditional operator with min() to make the code clean
> 
> Signed-off-by: You Kangren <youkangren@...o.com>
> ---
>  drivers/net/wireless/legacy/ray_cs.c | 3 +--
>  1 file changed, 1 insertion(+), 2 deletions(-)
> 
> diff --git a/drivers/net/wireless/legacy/ray_cs.c b/drivers/net/wireless/legacy/ray_cs.c
> index 8ace797ce951..96f34d90f601 100644
> --- a/drivers/net/wireless/legacy/ray_cs.c
> +++ b/drivers/net/wireless/legacy/ray_cs.c
> @@ -2086,8 +2086,7 @@ static void ray_rx(struct net_device *dev, ray_dev_t *local,
>                         rx_data(dev, prcs, pkt_addr, rx_len);
> 
>                 copy_from_rx_buff(local, (UCHAR *) &local->last_bcn, pkt_addr,
> -                                 rx_len < sizeof(struct beacon_rx) ?
> -                                 rx_len : sizeof(struct beacon_rx));
> +                                 min(rx_len, sizeof(struct beacon_rx));

Hi You Kangren,

I like where you are going with this patch.
But unfortunately using min() here causes an x86_64 allmodconfig W=1 build
to fail with both gcc-12 and clang-16.

Perhaps min_t() would be more appropriate?

GCC 12.3.0 says:

In file included from ./include/linux/kernel.h:27,
                 from ./arch/x86/include/asm/percpu.h:27,
                 from ./arch/x86/include/asm/nospec-branch.h:14,
                 from ./arch/x86/include/asm/paravirt_types.h:27,
                 from ./arch/x86/include/asm/ptrace.h:97,
                 from ./arch/x86/include/asm/math_emu.h:5,
                 from ./arch/x86/include/asm/processor.h:13,
                 from ./arch/x86/include/asm/timex.h:5,
                 from ./include/linux/timex.h:67,
                 from ./include/linux/time32.h:13,
                 from ./include/linux/time.h:60,
                 from ./include/linux/stat.h:19,
                 from ./include/linux/module.h:13,
                 from drivers/net/wireless/legacy/ray_cs.c:20:
drivers/net/wireless/legacy/ray_cs.c: In function 'ray_rx':
./include/linux/minmax.h:20:35: warning: comparison of distinct pointer types lacks a cast
   20 |         (!!(sizeof((typeof(x) *)1 == (typeof(y) *)1)))
      |                                   ^~
./include/linux/minmax.h:26:18: note: in expansion of macro '__typecheck'
   26 |                 (__typecheck(x, y) && __no_side_effects(x, y))
      |                  ^~~~~~~~~~~
./include/linux/minmax.h:36:31: note: in expansion of macro '__safe_cmp'
   36 |         __builtin_choose_expr(__safe_cmp(x, y), \
      |                               ^~~~~~~~~~
./include/linux/minmax.h:67:25: note: in expansion of macro '__careful_cmp'
   67 | #define min(x, y)       __careful_cmp(x, y, <)
      |                         ^~~~~~~~~~~~~
drivers/net/wireless/legacy/ray_cs.c:2089:35: note: in expansion of macro 'min'
 2089 |                                   min(rx_len, sizeof(struct beacon_rx));
      |                                   ^~~
drivers/net/wireless/legacy/ray_cs.c:2089:72: error: expected ')' before ';' token
 2089 |                                   min(rx_len, sizeof(struct beacon_rx));
      |                                                                        ^
drivers/net/wireless/legacy/ray_cs.c:2088:34: note: to match this '('
 2088 |                 copy_from_rx_buff(local, (UCHAR *) &local->last_bcn, pkt_addr,
      |                                  ^
drivers/net/wireless/legacy/ray_cs.c:2098:23: error: expected ';' before '}' token
 2098 |                 break;
      |                       ^
      |                       ;
 2099 |         }
      |         ~