On Wed, May 06, 2026 at 02:25:23PM +0800, Abdul Rahim, Faizal wrote: > > > On 30/4/2026 9:50 pm, Simon Horman wrote: > > From: 'Simon Horman' <[email protected]> > > > > This is an AI-generated review of your patch. The human sending this > > email has considered the AI review valid, or at least plausible. > > Full review at: https://sashiko.dev > > --- > > 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? > > > > Yes you're right, thanks, will update. > > >> +} > > [ ... ] > >> @@ -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? > > Will update. > > > > >> 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? > > > > Hi Simon, you've raised this issue in v2, and after discussion, you've > agreed that this change doesn't belong in this patch series. > > Not sure if I missed anything?
Sorry, my bad. I missed that we'd already covered this one.
