netdev - Re: [PATCH] net: netcp: MAX_SKB

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Date:   Fri, 31 Mar 2023 18:58:25 +0200
From:   Eric Dumazet <edumazet@...gle.com>
To:     Alexander Lobakin <aleksander.lobakin@...el.com>
Cc:     Arnd Bergmann <arnd@...nel.org>, Jakub Kicinski <kuba@...nel.org>,
        Arnd Bergmann <arnd@...db.de>,
        "David S. Miller" <davem@...emloft.net>,
        Paolo Abeni <pabeni@...hat.com>,
        Nikolay Aleksandrov <razor@...ckwall.org>,
        Jason Xing <kerneljasonxing@...il.com>, netdev@...r.kernel.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH] net: netcp: MAX_SKB_FRAGS is now 'int'

On Fri, Mar 31, 2023 at 5:08 PM Alexander Lobakin
<aleksander.lobakin@...el.com> wrote:
>
> From: Arnd Bergmann <arnd@...nel.org>
> Date: Fri, 31 Mar 2023 09:48:56 +0200
>
> > From: Arnd Bergmann <arnd@...db.de>
> >
> > The type of MAX_SKB_FRAGS has changed recently, so the debug printk
> > needs to be updated:
> >
> > drivers/net/ethernet/ti/netcp_core.c: In function 'netcp_create_interface':
> > drivers/net/ethernet/ti/netcp_core.c:2084:30: error: format '%ld' expects argument of type 'long int', but argument 3 has type 'int' [-Werror=format=]
> >  2084 |                 dev_err(dev, "tx-pool size too small, must be at least %ld\n",
> >       |                              ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
> >
> > Fixes: 3948b05950fd ("net: introduce a config option to tweak MAX_SKB_FRAGS")
> > Signed-off-by: Arnd Bergmann <arnd@...db.de>
> > ---
> >  drivers/net/ethernet/ti/netcp_core.c | 2 +-
> >  1 file changed, 1 insertion(+), 1 deletion(-)
> >
> > diff --git a/drivers/net/ethernet/ti/netcp_core.c b/drivers/net/ethernet/ti/netcp_core.c
> > index 1bb596a9d8a2..dfdbcdeb991f 100644
> > --- a/drivers/net/ethernet/ti/netcp_core.c
> > +++ b/drivers/net/ethernet/ti/netcp_core.c
> > @@ -2081,7 +2081,7 @@ static int netcp_create_interface(struct netcp_device *netcp_device,
> >       netcp->tx_pool_region_id = temp[1];
> >
> >       if (netcp->tx_pool_size < MAX_SKB_FRAGS) {
> > -             dev_err(dev, "tx-pool size too small, must be at least %ld\n",
> > +             dev_err(dev, "tx-pool size too small, must be at least %d\n",
> >                       MAX_SKB_FRAGS);
> >               ret = -ENODEV;
> >               goto quit;
>
> (not related to the actual fix)
>
> I'd personally define %MAX_SKB_FRAGS as `(u32)CONFIG_MAX_SKB_FRAGS`.
> It can't be below zero or above %U32_MAX and we have to define it
> manually anyway, so why not cast to the type expected from it :D
>

Some files have the assumption MAX_SKB_FRAGS can be understood by the
C preprocessor.

#if MAX_SKB_FRAGS > 32
...

Kconfig does not allow to define unsigned int.
That would be the easiest way really...