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From: "Théo Lebrun" <theo.lebrun@bootlin.com>
To: Andrew Lunn <andrew+netdev@lunn.ch>,
	 "David S. Miller" <davem@davemloft.net>,
	Eric Dumazet <edumazet@google.com>,
	 Jakub Kicinski <kuba@kernel.org>,
	Paolo Abeni <pabeni@redhat.com>,  Rob Herring <robh@kernel.org>,
	Krzysztof Kozlowski <krzk+dt@kernel.org>,
	 Conor Dooley <conor+dt@kernel.org>,
	 Nicolas Ferre <nicolas.ferre@microchip.com>,
	 Claudiu Beznea <claudiu.beznea@tuxon.dev>,
	 Geert Uytterhoeven <geert@linux-m68k.org>,
	 Harini Katakam <harini.katakam@xilinx.com>,
	 Richard Cochran <richardcochran@gmail.com>,
	 Russell King <linux@armlinux.org.uk>
Cc: netdev@vger.kernel.org, devicetree@vger.kernel.org,
	linux-kernel@vger.kernel.org,
	"Thomas Petazzoni" <thomas.petazzoni@bootlin.com>,
	"Tawfik Bayouk" <tawfik.bayouk@mobileye.com>,
	"Théo Lebrun" <theo.lebrun@bootlin.com>,
	"Sean Anderson" <sean.anderson@linux.dev>
Subject: [PATCH net v4 5/5] net: macb: avoid double endianness swap in macb_set_hwaddr()
Date: Wed, 20 Aug 2025 16:55:09 +0200	[thread overview]
Message-ID: <20250820-macb-fixes-v4-5-23c399429164@bootlin.com> (raw)
In-Reply-To: <20250820-macb-fixes-v4-0-23c399429164@bootlin.com>

writel() does a CPU->LE conversion. Drop manual cpu_to_le*() calls.

On little-endian system:
 - cpu_to_le32() is a no-op (LE->LE),
 - writel() is a no-op (LE->LE),
 - dev_addr will therefore not be swapped and written as-is.

On big-endian system:
 - cpu_to_le32() is a swap (BE->LE),
 - writel() is a swap (BE->LE),
 - dev_addr will therefore be swapped twice and written as a BE value.

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]
   ...

Fixes: 89e5785fc8a6 ("[PATCH] Atmel MACB ethernet driver")
Reviewed-by: Sean Anderson <sean.anderson@linux.dev>
Signed-off-by: Théo Lebrun <theo.lebrun@bootlin.com>
---
 drivers/net/ethernet/cadence/macb_main.c | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/drivers/net/ethernet/cadence/macb_main.c b/drivers/net/ethernet/cadence/macb_main.c
index 7f31f264a6d342ea01e2f61944b12c9b9a3fe66e..fe319d77f2a8f6b1f3b698e0d11781936345ea8f 100644
--- a/drivers/net/ethernet/cadence/macb_main.c
+++ b/drivers/net/ethernet/cadence/macb_main.c
@@ -274,9 +274,9 @@ static void macb_set_hwaddr(struct macb *bp)
 	u32 bottom;
 	u16 top;
 
-	bottom = cpu_to_le32(*((u32 *)bp->dev->dev_addr));
+	bottom = *((u32 *)bp->dev->dev_addr);
 	macb_or_gem_writel(bp, SA1B, bottom);
-	top = cpu_to_le16(*((u16 *)(bp->dev->dev_addr + 4)));
+	top = *((u16 *)(bp->dev->dev_addr + 4));
 	macb_or_gem_writel(bp, SA1T, top);
 
 	if (gem_has_ptp(bp)) {

-- 
2.50.1


  parent reply	other threads:[~2025-08-20 14:56 UTC|newest]

Thread overview: 13+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2025-08-20 14:55 [PATCH net v4 0/5] net: macb: various fixes Théo Lebrun
2025-08-20 14:55 ` [PATCH net v4 1/5] dt-bindings: net: cdns,macb: allow tsu_clk without tx_clk Théo Lebrun
2025-08-26  9:25   ` Nicolas Ferre
2025-08-20 14:55 ` [PATCH net v4 2/5] net: macb: remove illusion about TBQPH/RBQPH being per-queue Théo Lebrun
2025-08-26  9:27   ` Nicolas Ferre
2025-08-20 14:55 ` [PATCH net v4 3/5] net: macb: move ring size computation to functions Théo Lebrun
2025-08-26  9:30   ` Nicolas Ferre
2025-08-20 14:55 ` [PATCH net v4 4/5] net: macb: single dma_alloc_coherent() for DMA descriptors Théo Lebrun
2025-08-26 15:23   ` Nicolas Ferre
2025-08-20 14:55 ` Théo Lebrun [this message]
2025-08-20 15:25   ` [PATCH net v4 5/5] net: macb: avoid double endianness swap in macb_set_hwaddr() Russell King (Oracle)
2025-09-05  9:02     ` Théo Lebrun
2025-08-20 15:03 ` [PATCH net v4 0/5] net: macb: various fixes Théo Lebrun

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