We expect the SFP write accessors to return the number of written bytes.
We fail to do so for single-byte smbus accesses, which may cause errors
when setting a module's high-power state and for some cotsworks modules.

Let's return the amount of written bytes, as expected.

Fixes: 7662abf4db94 ("net: phy: sfp: Add support for SMBus module access")
Signed-off-by: Maxime Chevallier <maxime.chevallier@bootlin.com>
---
 drivers/net/phy/sfp.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/drivers/net/phy/sfp.c b/drivers/net/phy/sfp.c
index 6166e9196364..84bef5099dda 100644
--- a/drivers/net/phy/sfp.c
+++ b/drivers/net/phy/sfp.c
@@ -765,7 +765,7 @@ static int sfp_smbus_byte_write(struct sfp *sfp, bool a2, u8 dev_addr,
 		dev_addr++;
 	}
 
-	return 0;
+	return data - (u8 *)buf;
 }
 
 static int sfp_i2c_configure(struct sfp *sfp, struct i2c_adapter *i2c)
-- 
2.49.0

On Mon, Jan 05, 2026 at 04:18:39PM +0100, Maxime Chevallier wrote:
> We expect the SFP write accessors to return the number of written bytes.
> We fail to do so for single-byte smbus accesses, which may cause errors
> when setting a module's high-power state and for some cotsworks modules.
> 
> Let's return the amount of written bytes, as expected.
> 
> Fixes: 7662abf4db94 ("net: phy: sfp: Add support for SMBus module access")
> Signed-off-by: Maxime Chevallier <maxime.chevallier@bootlin.com>

Reviewed-by: Andrew Lunn <andrew@lunn.ch>

    Andrew