From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-1.web.codeaurora.org [10.30.226.201]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id A549F35958; Thu, 30 Apr 2026 13:51:26 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=10.30.226.201 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1777557086; cv=none; b=CenrEIt5CU1OBATXayEMfjy8aCx/onmRuLxicJ+UgcR+4OTcU3ytl4stNSwjUxMNxV3FWG1yzWBvOp9fnxviynzqmxVm0vTpA5MA56WmtIBm1OwB69WgukFrfos9+/B+Y7ReH49bvqawAd+F5x45d/SGi9ln3KsNwLXGgmbY0kg= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1777557086; c=relaxed/simple; bh=sGKecohrPFm0s7IoeAxyxJmKcE8tQ35JCJLbT5iR9m8=; h=From:To:Cc:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version; b=jxptVzgDq0W7auao0v00tH1JDtjUh/d5+PfDNY0z137ZHgxsjDnKVlN8Fyp05lB71nSzL1D0mR/YCAsK8CMaXPm25jX3RQflpxpJtVU+XEoom0Ri84GSlHnWbSzchpKpZ7vYAJZIHBfZAtc21F7v/EYDnZGLlhefaYPzHXfaDFg= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=abCfbkoz; arc=none smtp.client-ip=10.30.226.201 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b="abCfbkoz" Received: by smtp.kernel.org (Postfix) with ESMTPSA id BC959C2BCB3; Thu, 30 Apr 2026 13:51:22 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1777557085; bh=sGKecohrPFm0s7IoeAxyxJmKcE8tQ35JCJLbT5iR9m8=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=abCfbkozqqeclATf5iyy8Ha/AMdrHQ3m0RD8bvbJIyrPqg+uVcr4sO2JtNVvAcXQ2 FPitsgA0/L+mbeCgryRresXrbPEC1qRrBGA/ldr5+8LT7j0nr9WYTD4O6e93rsn4Ia gTi5g0IXuljAIKwHuhwKn7Sw+Wp2pBdb44W6JpA7p4C/V3aeW0baSLoK9qFj4pMi0k YGTgV7UpUCNw/N31Nd8XjyFY9llWLwEHHSaijxwH+Fe4ft/j/3iRRdvFet4qqm5QK/ AR8x/a1MXEQ4hVkqCAwy00DypdxgIsE6AYT5mn60s5UUfs7yCwUfUqp/TUCucbI/DZ T/Wep7zefQqvQ== From: Simon Horman To: khai.wen.tan@linux.intel.com Cc: 'Simon Horman' , anthony.l.nguyen@intel.com, andrew+netdev@lunn.ch, davem@davemloft.net, edumazet@google.com, kuba@kernel.org, pabeni@redhat.com, intel-wired-lan@lists.osuosl.org, netdev@vger.kernel.org, linux-kernel@vger.kernel.org, faizal.abdul.rahim@intel.com, hong.aun.looi@intel.com, khai.wen.tan@intel.com, faizal.abdul.rahim@linux.intel.com Subject: Re: [PATCH iwl-next v4 3/3] igc: add support for forcing link speed without autonegotiation Date: Thu, 30 Apr 2026 14:50:57 +0100 Message-ID: <20260430135057.1653330-1-horms@kernel.org> X-Mailer: git-send-email 2.53.0 In-Reply-To: <20260428060009.311393-4-khai.wen.tan@linux.intel.com> References: <20260428060009.311393-4-khai.wen.tan@linux.intel.com> Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit From: 'Simon Horman' 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? > +} [ ... ] > @@ -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) {