Re: [PATCH net] net: phy: phy_caps: Don't skip better duplex macth on non-exact match

Larysa Zaremba
2025-06-03T13:11:50Z

On Tue, Jun 03, 2025 at 10:35:40AM +0200, Maxime Chevallier wrote:
> When performing a non-exact phy_caps lookup, we are looking for a
> supported mode that matches as closely as possible the passed speed/duplex.
>
> Blamed patch broke that logic by returning a match too early in case
> the caller asks for half-duplex, as a full-duplex linkmode may match
> first, and returned as a non-exact match without even trying to mach on
> half-duplex modes.
>
> Reported-by: Jijie Shao <shaojijie@huawei.com>
> Closes: https://lore.kernel.org/netdev/20250603102500.4ec743cf@fedora/T/#m22ed60ca635c67dc7d9cbb47e8995b2beb5c1576
> Fixes: fc81e257d19f ("net: phy: phy_caps: Allow looking-up link caps based on speed and duplex")
> Signed-off-by: Maxime Chevallier <maxime.chevallier@bootlin.com>

Reviewed-by: Larysa Zaremba <larysa.zaremba@intel.com>

> ---
> drivers/net/phy/phy_caps.c | 15 +++++++++------
> 1 file changed, 9 insertions(+), 6 deletions(-)
>
> diff --git a/drivers/net/phy/phy_caps.c b/drivers/net/phy/phy_caps.c
> index 703321689726..d80f6a37edf1 100644
> --- a/drivers/net/phy/phy_caps.c
> +++ b/drivers/net/phy/phy_caps.c
> @@ -195,7 +195,7 @@ const struct link_capabilities *
> phy_caps_lookup(int speed, unsigned int duplex, const unsigned long *supported,
> bool exact)
> {
> - const struct link_capabilities *lcap, *last = NULL;
> + const struct link_capabilities *lcap, *match = NULL, *last = NULL;
>
> for_each_link_caps_desc_speed(lcap) {
> if (linkmode_intersects(lcap->linkmodes, supported)) {
> @@ -204,16 +204,19 @@ phy_caps_lookup(int speed, unsigned int duplex, const unsigned long *supported,
> if (lcap->speed == speed && lcap->duplex == duplex) {
> return lcap;
> } else if (!exact) {
> - if (lcap->speed <= speed)
> - return lcap;
> + if (!match && lcap->speed <= speed)
> + match = lcap;
> +
> + if (lcap->speed < speed)
> + break;
> }
> }
> }
>
> - if (!exact)
> - return last;
> + if (!match && !exact)
> + match = last;
>
> - return NULL;
> + return match;
> }
> EXPORT_SYMBOL_GPL(phy_caps_lookup);
>
> --
> 2.49.0
>
>