[PATCH net-next v5 07/13] net: phy: phy_caps: Allow looking-up link caps based on speed and duplex

[Russell King (Oracle)]

On Thu, May 29, 2025 at 05:36:11PM +0800, Jijie Shao wrote:
> Hi Maxime,  fc81e257d19f ("net: phy: phy_caps: Allow looking-up link caps based on speed and duplex") might have different behavior than the modification.
> My case is set 10M Half with disable autoneg both sides and I expect it is
> link in 10M Half. But now, it is link in 10M Full，which is not what I
> expect.
> 
> I used followed command and trace how phy worked.
> 	ethtool -s eth1 autoneg off speed 10 duplex half
> The log is showed as followed:
> ethtool-13127	[067]	6164.771853: phy_ethtool_ksettings set: (phy_ethtool ksettings set+0x0/0x200) duplex=0 speed=10
> kworker/u322:2-11096	[070]	6164.771853:	_phy_start_aneq: ( _phy_start_aneg+0x0/0xb8) duplex=0 speed=10
> kworker/u322:2-11096	[070]	6164.771854:	phy_caps_lookup: (phy_caps_lookup+0x0/0xf0) duplex=0 speed=10
> kworker/u322:2-11096	[070]	6164.771855:	phy_config_aneg: (phy_config_aneg+0x0/0x70) duplex=1 speed=10
> kworker/u322:2-11096	[070]	6164.771856:	genphy_config_aneg:	(__genphy_config_aneg+0X0/0X270) duplex=1 speed=10
> 
> I also try to fixed it and it works. Do you have any idea about it.
> 
> diff --git a/drivers/net/phy/phy.c b/drivers/net/phy/phy.c
> index 0e762fc3a529..2986c41c42a8 100644
> --- a/drivers/net/phy/phy.c
> +++ b/drivers/net/phy/phy.c
> @@ -258,7 +258,7 @@ static void phy_sanitize_settings(struct phy_device *phydev)
>         const struct link_capabilities *c;
> 
>         c = phy_caps_lookup(phydev->speed, phydev->duplex, phydev->supported,
> -                           false);
> +                           true);

This isn't the correct fix, as:

+ * When @exact is not set, we return either an exact match, or matching capabilities
+ * at lower speed, or the lowest matching speed, or NULL.

So it isn't returning the exact match but apparently ignoring the
duplex.

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