linux-kernel - RE: [PATCH net-next 4/5] net: fec: remove rx_align from fec_enet

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Message-ID:
 <AS8PR04MB84973D6B08C8D8A37E71A8D688CCA@AS8PR04MB8497.eurprd04.prod.outlook.com>
Date: Wed, 12 Nov 2025 02:00:05 +0000
From: Wei Fang <wei.fang@....com>
To: Frank Li <frank.li@....com>
CC: Shenwei Wang <shenwei.wang@....com>, Clark Wang <xiaoning.wang@....com>,
	"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>,
	"eric@...int.com" <eric@...int.com>, "imx@...ts.linux.dev"
	<imx@...ts.linux.dev>, "netdev@...r.kernel.org" <netdev@...r.kernel.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: RE: [PATCH net-next 4/5] net: fec: remove rx_align from
 fec_enet_private

> On Tue, Nov 11, 2025 at 06:00:56PM +0800, Wei Fang wrote:
> > The rx_align was introduced by the commit 41ef84ce4c72 ("net: fec: change
> > FEC alignment according to i.mx6 sx requirement"). Because the i.MX6 SX
> > requires RX buffer must be 64 bytes alignment.
> >
> > Since the commit 95698ff6177b ("net: fec: using page pool to manage RX
> > buffers"), the address of the RX buffer is always the page address plus
> > 128 bytes, so RX buffer is always 64-byte aligned. Therefore, rx_align
> > has no effect since that commit, and we can safely remove it.
> 
> I suggest keep it as it because we need know this kind limitation in case
> future code change broke prediction
> 'net: fec: using page pool to manage RX ..."

We still have tx_align to get the limitation. Or we can add a comment
to doc the limitation. Invalid code in the driver is pointless.