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

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Message-ID: <17d518ca-d35a-4279-b4fe-6930c5e279cd@amd.com>
Date: Thu, 11 Sep 2025 08:43:32 +0530
From: "Karumanchi, Vineeth" <vineeth@....com>
To: Théo Lebrun <theo.lebrun@...tlin.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()

Hi Theo,

On 9/10/2025 9:45 PM, Théo Lebrun wrote:
> bp->dev->dev_addr is of type `unsigned char *`. Casting it to a u32
> pointer and dereferencing implies dealing manually with endianness,
> which is error-prone.
> 
> Replace by calls to get_unaligned_le32|le16() helpers.
> 
> This was found using sparse:
>     ⟩ make C=2 drivers/net/ethernet/cadence/macb_main.o
>     warning: incorrect type in assignment (different base types)
>        expected unsigned int [usertype] bottom
>        got restricted __le32 [usertype]
>     warning: incorrect type in assignment (different base types)
>        expected unsigned short [usertype] top
>        got restricted __le16 [usertype]
>     ...
> 
> Reviewed-by: Sean Anderson <sean.anderson@...ux.dev>
> Signed-off-by: Théo Lebrun <theo.lebrun@...tlin.com>
> ---
>   drivers/net/ethernet/cadence/macb_main.c | 6 ++----
>   1 file changed, 2 insertions(+), 4 deletions(-)
> 
> diff --git a/drivers/net/ethernet/cadence/macb_main.c b/drivers/net/ethernet/cadence/macb_main.c
> index fc082a7a5a313be3d58a008533c3815cb1b1639a..c16d60048185b4cb473ddfcf4633fa2f6dea20cc 100644
> --- a/drivers/net/ethernet/cadence/macb_main.c
> +++ b/drivers/net/ethernet/cadence/macb_main.c
> @@ -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.

> -	bottom = cpu_to_le32(*((u32 *)bp->dev->dev_addr));
>   	macb_or_gem_writel(bp, SA1B, bottom);
> -	top = cpu_to_le16(*((u16 *)(bp->dev->dev_addr + 4)));
>   	macb_or_gem_writel(bp, SA1T, top);
>   
>   	if (gem_has_ptp(bp)) {
> 

-- 
🙏 Vineeth