From nobody Thu Oct 2 10:55:27 2025 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 0A6E6306B13; Thu, 18 Sep 2025 12:59:36 +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=1758200377; cv=none; b=Jw43Ubf+Mxb5Py4826cLJ0e4xaWcuSkDMd8c+lXEoQTxq7pod/r9562UrWB80SLcNdzQr0Y5PE+ysakrQX5LA/g8bx0d+kMgZCFCmaen7otZBXCuQJA8AKz+4YOEUkMcLSO+s/RvrkADrOOEECikt60pL1vwUPkA2fvjUCrKuTk= ARC-Message-Signature: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1758200377; c=relaxed/simple; bh=gK7abQXc0cr8q5l7D1BR+bo/xg4UM1mzmwrdqOR2Vmg=; h=From:Date:Subject:MIME-Version:Content-Type:Message-Id:References: In-Reply-To:To:Cc; b=nzhLRTw3fXBWqo7sIyXxrnP3hlZVCR3Rb6DyL2V2LY5A2nXy2LQRShJUhZThin7xIPyXWcYgeQdWaLG6Mp2k2zLmAJR/FgIFr8LmUqeJY1t50807GAhLEnI0eTMFWaZmjLetWeri3isE57u/woJQH0aClthxNC0XAKIA62D3Nbk= ARC-Authentication-Results: i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=V+HKpYRY; 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="V+HKpYRY" Received: by smtp.kernel.org (Postfix) with ESMTPSA id D03D4C4CEE7; Thu, 18 Sep 2025 12:59:35 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1758200376; bh=gK7abQXc0cr8q5l7D1BR+bo/xg4UM1mzmwrdqOR2Vmg=; h=From:Date:Subject:References:In-Reply-To:To:Cc:From; b=V+HKpYRYfEVBMVoOK1kJ6evGvvOmJ9ccLpTy6jYwXp98WstRPkesnss5hcC+gVIz7 SN0xvxc7KB26xPhqq8lOQsPUtruqkGhPjkql/i52VWM+PldhI9jh3KDqFWTTAEFV28 hsIawK0cHZv8YXWXJEyGCEhcaY+aNL091qolO+xsDY3dk0RdxDZdfKQoR4XeF7oBOx vn2wuAE+ST184PxHtmn/OIJzAFYlVORU938Ey4rSC3XIJlGRyKofC8Pl0Nh3MqiK5d 8ocfL2g7FwpDdxEXJ7cC/6Rofv4DkcemujCB/OjmhEZzbCAxQpQBjBMpWycvVk7jyf ToJrYHV2tSJPQ== From: Vincent Mailhol Date: Thu, 18 Sep 2025 21:59:13 +0900 Subject: [PATCH RFC 3/5] can: populate the minimum and maximum MTU values Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset="utf-8" Content-Transfer-Encoding: quoted-printable Message-Id: <20250918-can-fix-mtu-v1-3-471edb942295@kernel.org> References: <20250918-can-fix-mtu-v1-0-471edb942295@kernel.org> In-Reply-To: <20250918-can-fix-mtu-v1-0-471edb942295@kernel.org> To: Oliver Hartkopp , Marc Kleine-Budde Cc: linux-can@vger.kernel.org, linux-kernel@vger.kernel.org, Vincent Mailhol X-Mailer: b4 0.14.2 X-Developer-Signature: v=1; a=openpgp-sha256; l=5070; i=mailhol@kernel.org; h=from:subject:message-id; bh=gK7abQXc0cr8q5l7D1BR+bo/xg4UM1mzmwrdqOR2Vmg=; b=owGbwMvMwCV2McXO4Xp97WbG02pJDBlnmHR/y1+5sNbSLDVllcwsk6fTm79skTpt7l+9xb345 Gt98bgTHaUsDGJcDLJiiizLyjm5FToKvcMO/bWEmcPKBDKEgYtTACaiGsfIMO/9f/vkLfN3vPjA fuf6m2mxzJ/iS58wcOaoyAjdqr1zehvDP7vKIxaasw6c9zaZ/94jN/HOkSL3zyuFrwlsEW3j3mv ynAsA X-Developer-Key: i=mailhol@kernel.org; a=openpgp; fpr=ED8F700574E67F20E574E8E2AB5FEB886DBB99C2 By populating: net_device->min_mtu and net_device->max_mtu the net core infrastructure will automatically: 1. validate that the user's inputs are in range. 2. report those min and max MTU values through the netlink interface. Add can_set_default_mtu() which will set the default mtu value as well as the minimum and maximum values. The logic for the default mtu value remains unchanged: - CANFD_MTU if the device has a static CAN_CTRLMODE_FD. - CAN_MTU otherwise. Call can_set_default_mtu() each time the CAN_CTRLMODE_FD is modified. This will guarantee that the MTU value is always consistent with the control mode flags. With this, the checks done in can_change_mtu() become fully redundant and will be removed in an upcoming change and it is now possible to confirm the minimum and maximum MTU values on a physical CAN interface by doing: $ ip --details link show can0 The virtual interfaces (vcan and vxcan) are not impacted by this change. Signed-off-by: Vincent Mailhol --- With this, when adding the CAN XL netlink interface, all we have to do is to add one if branch to can_set_default_mtu() like this: void can_set_default_mtu(struct net_device *dev) { struct can_priv *priv =3D netdev_priv(dev); if (priv->ctrlmode & CAN_CTRLMODE_XL) { dev->mtu =3D CANXL_MTU; dev->min_mtu =3D CANXL_MIN_MTU; dev->max_mtu =3D CANXL_MAX_MTU; } else if (priv->ctrlmode & CAN_CTRLMODE_FD) { dev->mtu =3D CANFD_MTU; dev->min_mtu =3D CANFD_MTU; dev->max_mtu =3D CANFD_MTU; } else { dev->mtu =3D CAN_MTU; dev->min_mtu =3D CAN_MTU; dev->max_mtu =3D CAN_MTU; } } and we will be done! --- drivers/net/can/dev/dev.c | 21 ++++++++++++++++++--- drivers/net/can/dev/netlink.c | 9 ++++----- include/linux/can/dev.h | 1 + 3 files changed, 23 insertions(+), 8 deletions(-) diff --git a/drivers/net/can/dev/dev.c b/drivers/net/can/dev/dev.c index a0ae659beedcd1fa0979662c12614ae7846032c0..69c00720e9956cad986ea86fbba= 49285d76f51db 100644 --- a/drivers/net/can/dev/dev.c +++ b/drivers/net/can/dev/dev.c @@ -239,11 +239,12 @@ EXPORT_SYMBOL_GPL(can_bus_off); void can_setup(struct net_device *dev) { dev->type =3D ARPHRD_CAN; - dev->mtu =3D CAN_MTU; dev->hard_header_len =3D 0; dev->addr_len =3D 0; dev->tx_queue_len =3D 10; =20 + can_set_default_mtu(dev); + /* New-style flags. */ dev->flags =3D IFF_NOARP; dev->features =3D NETIF_F_HW_CSUM; @@ -309,6 +310,21 @@ void free_candev(struct net_device *dev) } EXPORT_SYMBOL_GPL(free_candev); =20 +void can_set_default_mtu(struct net_device *dev) +{ + struct can_priv *priv =3D netdev_priv(dev); + + if (priv->ctrlmode & CAN_CTRLMODE_FD) { + dev->mtu =3D CANFD_MTU; + dev->min_mtu =3D CANFD_MTU; + dev->max_mtu =3D CANFD_MTU; + } else { + dev->mtu =3D CAN_MTU; + dev->min_mtu =3D CAN_MTU; + dev->max_mtu =3D CAN_MTU; + } +} + /* changing MTU and control mode for CAN/CANFD devices */ int can_change_mtu(struct net_device *dev, int new_mtu) { @@ -361,8 +377,7 @@ int can_set_static_ctrlmode(struct net_device *dev, u32= static_mode) priv->ctrlmode =3D static_mode; =20 /* override MTU which was set by default in can_setup()? */ - if (static_mode & CAN_CTRLMODE_FD) - dev->mtu =3D CANFD_MTU; + can_set_default_mtu(dev); =20 return 0; } diff --git a/drivers/net/can/dev/netlink.c b/drivers/net/can/dev/netlink.c index d9f6ab3efb9767409c318b714f19df8a30e51137..248f607e3864ffbda6f0b8daf4e= 2484179cf9cd5 100644 --- a/drivers/net/can/dev/netlink.c +++ b/drivers/net/can/dev/netlink.c @@ -223,17 +223,16 @@ static int can_changelink(struct net_device *dev, str= uct nlattr *tb[], priv->ctrlmode &=3D ~cm->mask; priv->ctrlmode |=3D maskedflags; =20 - /* CAN_CTRLMODE_FD can only be set when driver supports FD */ - if (priv->ctrlmode & CAN_CTRLMODE_FD) { - dev->mtu =3D CANFD_MTU; - } else { - dev->mtu =3D CAN_MTU; + /* Wipe potential leftovers from previous CAN FD config */ + if (!(priv->ctrlmode & CAN_CTRLMODE_FD)) { memset(&priv->fd.data_bittiming, 0, sizeof(priv->fd.data_bittiming)); priv->ctrlmode &=3D ~CAN_CTRLMODE_FD_TDC_MASK; memset(&priv->fd.tdc, 0, sizeof(priv->fd.tdc)); } =20 + can_set_default_mtu(dev); + fd_tdc_flag_provided =3D cm->mask & CAN_CTRLMODE_FD_TDC_MASK; /* CAN_CTRLMODE_TDC_{AUTO,MANUAL} are mutually * exclusive: make sure to turn the other one off diff --git a/include/linux/can/dev.h b/include/linux/can/dev.h index 5dc58360c2d74a1711d4e02d28fe52ae20b146e0..3354f70ed2c684d7d482549560d= 4cb5838cbebd5 100644 --- a/include/linux/can/dev.h +++ b/include/linux/can/dev.h @@ -166,6 +166,7 @@ struct can_priv *safe_candev_priv(struct net_device *de= v); =20 int open_candev(struct net_device *dev); void close_candev(struct net_device *dev); +void can_set_default_mtu(struct net_device *dev); int can_change_mtu(struct net_device *dev, int new_mtu); int __must_check can_set_static_ctrlmode(struct net_device *dev, u32 static_mode); --=20 2.49.1