netdev - RE: [PATCH v2] net: fec: account for VLAN header in frame length calculations

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Message-ID:
 <PAXPR04MB851065772CADABDB29F70BD88897A@PAXPR04MB8510.eurprd04.prod.outlook.com>
Date: Thu, 22 Jan 2026 06:07:27 +0000
From: Wei Fang <wei.fang@....com>
To: Clemens Gruber <mail@...mensgruber.at>
CC: Shenwei Wang <shenwei.wang@....com>, Clark Wang <xiaoning.wang@....com>,
	"imx@...ts.linux.dev" <imx@...ts.linux.dev>, "netdev@...r.kernel.org"
	<netdev@...r.kernel.org>, "stable@...nel.org" <stable@...nel.org>,
	"andrew+netdev@...n.ch" <andrew+netdev@...n.ch>, "davem@...emloft.net"
	<davem@...emloft.net>, "edumazet@...gle.com" <edumazet@...gle.com>,
	"kuba@...nel.org" <kuba@...nel.org>, "pabeni@...hat.com" <pabeni@...hat.com>
Subject: RE: [PATCH v2] net: fec: account for VLAN header in frame length
 calculations

> The MAX_FL (maximum frame length) and related calculations used
> ETH_HLEN,
> which does not account for the 4-byte VLAN tag in tagged frames. This
> caused the hardware to reject valid VLAN frames as oversized, resulting
> in RX errors and dropped packets.
> 
> Use VLAN_ETH_HLEN instead of ETH_HLEN in the MAX_FL register setup,
> cut-through mode threshold, buffer allocation, and max_mtu calculation.
> 
> Cc: stable@...nel.org # v6.18+
> Fixes: 62b5bb7be7bc ("net: fec: update MAX_FL based on the current MTU")
> Fixes: d466c16026e9 ("net: fec: enable the Jumbo frame support for
> i.MX8QM")
> Fixes: 59e9bf037d75 ("net: fec: add change_mtu to support dynamic buffer
> allocation")
> Fixes: ec2a1681ed4f ("net: fec: use a member variable for maximum buffer
> size")
> Signed-off-by: Clemens Gruber <mail@...mensgruber.at>
> ---
> Changes in v2:
> - Fix the other frame length calculations too
> - Improved title and commit message
> 
> One line in fec_restart (after the FEC_QUIRK_JUMBO_FRAME check) has now
> 82 characters but I think folding it would make it less readable.
> Let me know if this should be changed.
> ---

Thanks, this patch looks good to me.

Reviewed-by: Wei Fang <wei.fang@....com>