linux-kernel - Re: [PATCH net v5 5/5] net: macb: avoid dealing with endianness in macb_set

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Message-Id: <DCPV0SVDR2J7.2FKMD5PD9S235@bootlin.com>
Date: Thu, 11 Sep 2025 11:22:47 +0200
From: Théo Lebrun <theo.lebrun@...tlin.com>
To: "Karumanchi, Vineeth" <vineeth@....com>, "Andrew Lunn"
 <andrew+netdev@...n.ch>, "David S. Miller" <davem@...emloft.net>, "Eric
 Dumazet" <edumazet@...gle.com>, "Jakub Kicinski" <kuba@...nel.org>, "Paolo
 Abeni" <pabeni@...hat.com>, "Rob Herring" <robh@...nel.org>, "Krzysztof
 Kozlowski" <krzk+dt@...nel.org>, "Conor Dooley" <conor+dt@...nel.org>,
 "Nicolas Ferre" <nicolas.ferre@...rochip.com>, "Claudiu Beznea"
 <claudiu.beznea@...on.dev>, "Geert Uytterhoeven" <geert@...ux-m68k.org>,
 "Harini Katakam" <harini.katakam@...inx.com>, "Richard Cochran"
 <richardcochran@...il.com>, "Russell King" <linux@...linux.org.uk>
Cc: <netdev@...r.kernel.org>, <devicetree@...r.kernel.org>,
 <linux-kernel@...r.kernel.org>, "Thomas Petazzoni"
 <thomas.petazzoni@...tlin.com>, "Tawfik Bayouk"
 <tawfik.bayouk@...ileye.com>, "Sean Anderson" <sean.anderson@...ux.dev>
Subject: Re: [PATCH net v5 5/5] net: macb: avoid dealing with endianness in
 macb_set_hwaddr()

On Thu Sep 11, 2025 at 5:13 AM CEST, Karumanchi, Vineeth wrote:
> On 9/10/2025 9:45 PM, Théo Lebrun wrote:
>> @@ -271,12 +271,10 @@ static bool hw_is_gem(void __iomem *addr, bool native_io)
>>   
>>   static void macb_set_hwaddr(struct macb *bp)
>>   {
>> -	u32 bottom;
>> -	u16 top;
>> +	u32 bottom = get_unaligned_le32(bp->dev->dev_addr);
>> +	u16 top = get_unaligned_le16(bp->dev->dev_addr + 4);
>
> please change the order as per reverse xmas tree.

I had realised this before sending the patch but preferred keeping the
ordering as-is to access dev_addr+0 first then dev_addr+4.

RCT is a strict rule in net so I'll fix it in the next revision. Some
sneaky options were also considered: a spare space in the `u32 bottom`
line, express bottom using `dev_addr + 0`, or renaming variables. :-)

Thanks Vineeth,

--
Théo Lebrun, Bootlin
Embedded Linux and Kernel engineering
https://bootlin.com