From: David Laight <david.laight.linux@gmail.com>
To: Nicolai Buchwitz <nb@tipi-net.de>
Cc: "Jakub Kicinski" <kuba@kernel.org>,
"Théo Lebrun" <theo.lebrun@bootlin.com>,
"Conor Dooley" <conor.dooley@microchip.com>,
"Claudiu Beznea" <claudiu.beznea@tuxon.dev>,
"Jonathan Bell" <jonathan@raspberrypi.com>,
"Andrew Lunn" <andrew+netdev@lunn.ch>,
"David S . Miller" <davem@davemloft.net>,
"Eric Dumazet" <edumazet@google.com>,
"Paolo Abeni" <pabeni@redhat.com>,
"Richard Cochran" <richardcochran@gmail.com>,
netdev@vger.kernel.org, linux-kernel@vger.kernel.org
Subject: Re: [PATCH net 1/2] net: macb: exclude software FCS from TX byte statistics
Date: Fri, 28 Aug 2026 14:02:42 +0100 [thread overview]
Message-ID: <20260828140242.7c78d4cd@pumpkin> (raw)
In-Reply-To: <36165fe4a906b07dd9f92a73a72a05f1@tipi-net.de>
On Fri, 28 Aug 2026 10:20:24 +0200
Nicolai Buchwitz <nb@tipi-net.de> wrote:
> Hi Jakub
>
> On 27.8.2026 20:56, Jakub Kicinski wrote:
> > On Mon, 24 Aug 2026 15:47:02 +0200 Nicolai Buchwitz wrote:
> >> + * @skb_len: skb->len as handed over by the stack, before padding and
> >> + * software FCS, only set for the last buffer of the frame
> >
> > counting pad bytes to ETH_ZLEN as sent is perfectly legit,
> > it's a driver preference. Some don't because HW pads and
> > the driver doesn't want to bother adding a conditional.
> > But it's best if the driver bytes match wire bytes IMO.
>
> Matches what I had in mind for my v2. So the driver bytes would match
> wire bytes minus FCS.
>
> >
> > Either way, you only need u8 or even a flag for this,
> > not a full u32?
>
> Agreed. skb->len at completion should already do the trick (minus
> ETH_FCS_LEN).
> So a flag would be sufficient.
If you make the 'flag' 0 or 4 it will save some maths (and maybe a branch)
in the completion code.
David
>
> Thanks,
> Nicolai
>
next prev parent reply other threads:[~2026-08-28 13:02 UTC|newest]
Thread overview: 11+ messages / expand[flat|nested] mbox.gz Atom feed top
2026-08-24 13:47 [PATCH net 0/2] net: macb: fix zero UDPv4 checksum on transmit Nicolai Buchwitz
2026-08-24 13:47 ` [PATCH net 1/2] net: macb: exclude software FCS from TX byte statistics Nicolai Buchwitz
2026-08-25 15:04 ` Nicolai Buchwitz
2026-08-27 8:52 ` Paolo Abeni
2026-08-28 8:10 ` Nicolai Buchwitz
2026-08-27 18:56 ` Jakub Kicinski
2026-08-28 8:20 ` Nicolai Buchwitz
2026-08-28 13:02 ` David Laight [this message]
2026-08-28 8:37 ` David Laight
2026-08-24 13:47 ` [PATCH net 2/2] net: macb: fix zero UDPv4 checksum on transmit Nicolai Buchwitz
2026-08-28 6:04 ` [PATCH net 0/2] " Alexander Dahl
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