Thank you for your contribution! Sashiko AI review found 3 potential issue(s) to consider: - [High] Forcing half-duplex permanently clobbers the user's flow control preference. - [High] Missing validation for DUPLEX_UNKNOWN causes silent fallback to half-duplex. - [High] Ad-hoc synchronization loop using bit flags instead of a proper lock. --
commit 8d7b28f68d024d026b38dde450a1a1adfbbf8daf Author: Faizal Rahim <[email protected]> igc: add support for forcing link speed without autonegotiation This commit allows users to force 10/100 Mb/s link speed and duplex via ethtool when autonegotiation is disabled. Previously, the driver rejected these requests. > diff --git a/drivers/net/ethernet/intel/igc/igc_ethtool.c > b/drivers/net/ethernet/intel/igc/igc_ethtool.c > index cfcbf2fdad6e..9997ebbdf778 100644 > --- a/drivers/net/ethernet/intel/igc/igc_ethtool.c > +++ b/drivers/net/ethernet/intel/igc/igc_ethtool.c [ ... ] > @@ -2000,6 +2013,41 @@ static int igc_ethtool_get_link_ksettings(struct > net_device *netdev, > return 0; > } > > +/** > + * igc_handle_autoneg_disabled - Configure forced speed/duplex settings > + * @adapter: private driver structure > + * @speed: requested speed (must be SPEED_10 or SPEED_100) > + * @duplex: requested duplex > + * > + * Records forced speed/duplex when autoneg is disabled. > + * Caller must validate speed before calling this function. > + */ > +static void igc_handle_autoneg_disabled(struct igc_adapter *adapter, u32 > speed, > + u8 duplex) > +{ > + struct igc_mac_info *mac = &adapter->hw.mac; > + > + switch (speed) { > + case SPEED_10: > + mac->forced_speed_duplex = (duplex == DUPLEX_FULL) ? > + IGC_FORCED_10F : IGC_FORCED_10H; > + break; > + case SPEED_100: > + mac->forced_speed_duplex = (duplex == DUPLEX_FULL) ? > + IGC_FORCED_100F : IGC_FORCED_100H; > + break; > + default: > + WARN_ONCE(1, "Unsupported speed %u\n", speed); > + return; > + } > + > + mac->autoneg_enabled = false; > + > + /* Half-duplex cannot support flow control per IEEE 802.3 */ > + if (duplex != DUPLEX_FULL) > + adapter->hw.fc.requested_mode = igc_fc_none; Does this permanently overwrite the user's flow control preference? If half-duplex is requested, requested_mode is set to igc_fc_none. Because requested_mode represents the persistent state for the user's flow control preference, the user might permanently lose their configuration. If they later switch back to full-duplex, requested_mode remains igc_fc_none, and flow control stays disabled. Would it be better to dynamically override hw->fc.current_mode to igc_fc_none during link configuration instead of mutating requested_mode? > +} [ ... ] > @@ -2071,14 +2126,20 @@ igc_ethtool_set_link_ksettings(struct net_device > *netdev, > } > } > > + if (cmd->base.autoneg == AUTONEG_DISABLE && > + cmd->base.speed != SPEED_10 && cmd->base.speed != SPEED_100) { > + netdev_info(dev, "Unsupported speed for forced link\n"); > + return -EINVAL; > + } > + Should we also validate cmd->base.duplex here to prevent a fallback to half-duplex? If a user runs a command like "ethtool -s eth0 speed 100 autoneg off" while the link is down, ethtool queries and preserves the current duplex value, which is DUPLEX_UNKNOWN (0xff). In igc_handle_autoneg_disabled(), the code checks if duplex == DUPLEX_FULL, which evaluates to false, and forces the interface to 100 Mbps half-duplex. Could we explicitly check that cmd->base.duplex is either DUPLEX_HALF or DUPLEX_FULL and return -EINVAL otherwise? > while (test_and_set_bit(__IGC_RESETTING, &adapter->state)) > usleep_range(1000, 2000); This isn't a bug introduced by this patch, but does this ad-hoc synchronization loop reimplement locking without fairness or lockdep support? According to the Networking Subsystem Guidelines, using bit operations as a substitute for real locks violates core kernel locking rules and introduces potential races. Could this be replaced with a proper concurrency mechanism such as a mutex? > > - if (cmd->base.autoneg == AUTONEG_ENABLE) { > + if (cmd->base.autoneg == AUTONEG_ENABLE) > igc_handle_autoneg_enabled(adapter, cmd); > - } else { > - netdev_info(dev, "Force mode currently not supported\n"); > - } > + else > + igc_handle_autoneg_disabled(adapter, cmd->base.speed, > + cmd->base.duplex); > > /* MDI-X => 2; MDI => 1; Auto => 3 */ > if (cmd->base.eth_tp_mdix_ctrl) { -- Sashiko AI review ยท https://sashiko.dev/#/patchset/[email protected]?part=3
