netdev - Re: [PATCH v3 net-next 5/7] net: dsa: tag_rtl8_4: add realtek 8 byte protocol 4 tag

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Message-ID: <8da0a0ce-6f62-ca02-0b72-bcf5ff4ec493@bang-olufsen.dk>
Date:   Mon, 18 Oct 2021 07:58:40 +0000
From:   Alvin Šipraga <ALSI@...g-olufsen.dk>
To:     DENG Qingfang <dqfext@...il.com>,
        Alvin Šipraga <alvin@...s.dk>
CC:     Linus Walleij <linus.walleij@...aro.org>,
        Andrew Lunn <andrew@...n.ch>,
        Vivien Didelot <vivien.didelot@...il.com>,
        Florian Fainelli <f.fainelli@...il.com>,
        Vladimir Oltean <olteanv@...il.com>,
        "David S. Miller" <davem@...emloft.net>,
        Jakub Kicinski <kuba@...nel.org>,
        Rob Herring <robh+dt@...nel.org>,
        Heiner Kallweit <hkallweit1@...il.com>,
        Russell King <linux@...linux.org.uk>,
        "netdev@...r.kernel.org" <netdev@...r.kernel.org>,
        "devicetree@...r.kernel.org" <devicetree@...r.kernel.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH v3 net-next 5/7] net: dsa: tag_rtl8_4: add realtek 8 byte
 protocol 4 tag

On 10/16/21 8:04 AM, DENG Qingfang wrote:
> On Fri, Oct 15, 2021 at 07:10:26PM +0200, Alvin Šipraga wrote:
>> +static struct sk_buff *rtl8_4_tag_xmit(struct sk_buff *skb,
>> +				       struct net_device *dev)
>> +{
>> +	struct dsa_port *dp = dsa_slave_to_port(dev);
>> +	__be16 *tag;
>> +
>> +	/* Pad out so the (stripped) packet is at least 64 bytes long
>> +	 * (including FCS), otherwise the switch will drop the packet.
>> +	 * Then we need an additional 8 bytes for the Realtek tag.
>> +	 */
>> +	if (unlikely(__skb_put_padto(skb, ETH_ZLEN + RTL8_4_TAG_LEN, false)))
>> +		return NULL;
> 
> Is this still required if you set rtl8365mb_cpu_rxlen to 64 bytes already?

Apparently not - nice catch. I've removed it for what will be v4. :)

> 
>> +
>> +	skb_push(skb, RTL8_4_TAG_LEN);
>> +