linux-kernel - Re: [PATCH v4] net: stmmac: fix maxmtu assignment to be within valid range

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Date:   Sat, 7 Jan 2017 02:12:23 +0200
From:   Andy Shevchenko <andy.shevchenko@...il.com>
To:     "Kweh, Hock Leong" <hock.leong.kweh@...el.com>
Cc:     "David S. Miller" <davem@...emloft.net>,
        Joao Pinto <Joao.Pinto@...opsys.com>,
        Giuseppe CAVALLARO <peppe.cavallaro@...com>,
        seraphin.bonnaffe@...com, Jarod Wilson <jarod@...hat.com>,
        Alexandre TORGUE <alexandre.torgue@...il.com>,
        Joachim Eastwood <manabian@...il.com>,
        Niklas Cassel <niklas.cassel@...s.com>,
        Johan Hovold <johan@...nel.org>, Pavel Machek <pavel@....cz>,
        lars.persson@...s.com, netdev <netdev@...r.kernel.org>,
        LKML <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH v4] net: stmmac: fix maxmtu assignment to be within valid range

On Sat, Jan 7, 2017 at 10:10 AM, Kweh, Hock Leong
<hock.leong.kweh@...el.com> wrote:
> From: "Kweh, Hock Leong" <hock.leong.kweh@...el.com>
>
> There is no checking valid value of maxmtu when getting it from device tree.
> This resolution added the checking condition to ensure the assignment is
> made within a valid range.

> changelog v4:
> * add print warning message when maxmtu > max_mtu as well

Yep.

> * add maxmtu = JUMBO_LEN into each *_default_data() at stmmac_pci.c

Yep.

But see comment below.

P.S. And perhaps next time send into our internal mailing list first for review.

> @@ -3345,8 +3345,14 @@ int stmmac_dvr_probe(struct device *device,
>                 ndev->max_mtu = JUMBO_LEN;
>         else
>                 ndev->max_mtu = SKB_MAX_HEAD(NET_SKB_PAD + NET_IP_ALIGN);
> -       if (priv->plat->maxmtu < ndev->max_mtu)
> +       if ((priv->plat->maxmtu < ndev->max_mtu) &&
> +           (priv->plat->maxmtu >= ndev->min_mtu))
>                 ndev->max_mtu = priv->plat->maxmtu;

> +       else if ((priv->plat->maxmtu < ndev->min_mtu) ||
> +                (priv->plat->maxmtu > ndev->max_mtu))
> +               netdev_warn(priv->dev,

What is the difference to just 'else'? (Returning back to my initial
proposal, I don't remember telling anything about 'else if' concept)

> +                           "%s: warning: maxmtu having invalid value (%d)\n",
> +                           __func__, priv->plat->maxmtu);

-- 
With Best Regards,
Andy Shevchenko