linux-kernel - Re: [PATCH linux-next] net: smc911x: replace ternary operator with min()

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Date:   Wed, 18 May 2022 17:38:54 +0200
From:   Geert Uytterhoeven <geert@...ux-m68k.org>
To:     Jakub Kicinski <kuba@...nel.org>
Cc:     Guo Zhengkui <guozhengkui@...o.com>,
        "David S. Miller" <davem@...emloft.net>,
        Eric Dumazet <edumazet@...gle.com>,
        Paolo Abeni <pabeni@...hat.com>,
        Colin Ian King <colin.king@...el.com>,
        Jiasheng Jiang <jiasheng@...as.ac.cn>,
        "open list:NETWORKING DRIVERS" <netdev@...r.kernel.org>,
        open list <linux-kernel@...r.kernel.org>,
        zhengkui_guo@...look.com
Subject: Re: [PATCH linux-next] net: smc911x: replace ternary operator with min()

Hi Jakub,

On Wed, May 18, 2022 at 5:33 PM Jakub Kicinski <kuba@...nel.org> wrote:
> On Wed, 18 May 2022 11:07:08 +0200 Geert Uytterhoeven wrote:
> > On Mon, May 16, 2022 at 10:36 PM Guo Zhengkui <guozhengkui@...o.com> wrote:
> > > Fix the following coccicheck warning:
> > >
> > > drivers/net/ethernet/smsc/smc911x.c:483:20-22: WARNING opportunity for min()
> > >
> > > Signed-off-by: Guo Zhengkui <guozhengkui@...o.com>
> >
> > Thanks for your patch, which is now commit 5ff0348b7f755aac ("net:
> > smc911x: replace ternary operator with min()") in net-next/master.
> >
> > > --- a/drivers/net/ethernet/smsc/smc911x.c
> > > +++ b/drivers/net/ethernet/smsc/smc911x.c
> > > @@ -480,7 +480,7 @@ static void smc911x_hardware_send_pkt(struct net_device *dev)
> > >         SMC_SET_TX_FIFO(lp, cmdB);
> > >
> > >         DBG(SMC_DEBUG_PKTS, dev, "Transmitted packet\n");
> > > -       PRINT_PKT(buf, len <= 64 ? len : 64);
> > > +       PRINT_PKT(buf, min(len, 64));
> >
> > Unfortunately you forgot to test-compile this with
> > ENABLE_SMC_DEBUG_PKTS=1, which triggers:
> >
> >         drivers/net/ethernet/smsc/smc911x.c: In function
> > ‘smc911x_hardware_send_pkt’:
> >         include/linux/minmax.h:20:28: error: comparison of distinct
> > pointer types lacks a cast [-Werror]
> >            20 |  (!!(sizeof((typeof(x) *)1 == (typeof(y) *)1)))
> >               |                            ^~
> >         drivers/net/ethernet/smsc/smc911x.c:483:17: note: in expansion
> > of macro ‘min’
> >           483 |  PRINT_PKT(buf, min(len, 64));
> >
> > "len" is "unsigned int", while "64" is "(signed) int".
>
> Ah, damn. I did double check that the build test actually compiles
> smc911x.o 'cause this patch looked suspicious. Didn't realize that
> more than allmodconfig is needed to trigger this :/
>
> How do you enable ENABLE_SMC_DEBUG_PKTS? You edit the source?

Yes you do.

To avoid missing stuff like this in the future, my fix also includes
a change to the dummy PRINT_PKT(), so you don't have to enable
ENABLE_SMC_DEBUG_PKTS anymore to trigger the issue.

> > I have sent a fix
> > https://lore.kernel.org/r/ca032d4122fc70d3a56a524e5944a8eff9a329e8.1652864652.git.geert+renesas@glider.be/
>
> Thanks a lot!

Gr{oetje,eeting}s,

                        Geert

--
Geert Uytterhoeven -- There's lots of Linux beyond ia32 -- geert@...ux-m68k.org

In personal conversations with technical people, I call myself a hacker. But
when I'm talking to journalists I just say "programmer" or something like that.
                                -- Linus Torvalds