From nobody Thu Oct 2 04:44:07 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 04C2630FC31; Tue, 23 Sep 2025 06:37:34 +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=1758609455; cv=none; b=YCLnx/9pa4MiH3buQaaUq4kw4u7yt0q0D53vyKVwIw8sleY9SbsAaFWRGQ1+nkDE02UIqGlToslrv697y8i03Do5J1I9w9r1AwM2BcM8WS3RsdNUh/QcgEfBt9BrFx/sKvlmrHc4ZxGSl2U80UtpDiIqhctO/hv65u2WVZUjycw= ARC-Message-Signature: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1758609455; c=relaxed/simple; bh=Zj00qJ2G6wtMCMGxh6W71gJtBiAdkMplYJcXlpTDfLk=; h=From:Date:Subject:MIME-Version:Content-Type:Message-Id:References: In-Reply-To:To:Cc; b=ujZQj6AfP65kd/j/vY1AC5aGhaXHle8Z7eOzpc3VZTO7cxc1kos3wSaApJRMQYf4XycSL7LkFKCNItP0EHPx51dJjZP4j+1zXM9eCiUAtrZlXuwGUE7FK+Ns4cjb6jzFXuMwocriAw+lPhU/IDeqLz/BA+VWd/Lgm9qse7coGOg= ARC-Authentication-Results: i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=n8b+MyuS; 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="n8b+MyuS" Received: by smtp.kernel.org (Postfix) with ESMTPSA id C6EACC116C6; Tue, 23 Sep 2025 06:37:33 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1758609454; bh=Zj00qJ2G6wtMCMGxh6W71gJtBiAdkMplYJcXlpTDfLk=; h=From:Date:Subject:References:In-Reply-To:To:Cc:From; b=n8b+MyuS6imcQOdMqgNNuhsbO4ZAbypL849gCYMzQ1hE8OqmGxXNYQvkzCqUGuikS N9tayWi1P6/CEDKcqrInjB5DYR+fdxHhcR9r6WQ4l5s1cn8RnKNJfK2NGpR1hn8juP pgYiAl76sseJi8n0y02VPCA2j5hO6R9qu+P45LCQESCcjERaHvj+QveFVXdRtdBSY3 pwX89xmLvlJSpQTG6Cyjicitu2FgMzKBslq6TWUvdYCniHF/rZESFuGQ2WWTYcTeg3 u/EQiliBu5JY57ReShiX52yuzchrbQqXbbKrSey/RZLNsQ/uhuT/iAteYXtvnRAlmX QBC4wizU6i6yQ== From: Vincent Mailhol Date: Tue, 23 Sep 2025 15:37:10 +0900 Subject: [PATCH v3 3/4] 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: <20250923-can-fix-mtu-v3-3-581bde113f52@kernel.org> References: <20250923-can-fix-mtu-v3-0-581bde113f52@kernel.org> In-Reply-To: <20250923-can-fix-mtu-v3-0-581bde113f52@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=5119; i=mailhol@kernel.org; h=from:subject:message-id; bh=Zj00qJ2G6wtMCMGxh6W71gJtBiAdkMplYJcXlpTDfLk=; b=owGbwMvMwCV2McXO4Xp97WbG02pJDBmXHFR4v/psVUjasIOZfZfXp2JuK8UCnczjc39997927 0L0rA26HaUsDGJcDLJiiizLyjm5FToKvcMO/bWEmcPKBDKEgYtTACYy6Sojw6tns5K3dvLu2H32 9uF/DJ8eHNHRYLG6EaabxDR54ndLASOG/0nrFt8z7nZ8slKEq1b5wvn5icZzT/bqNS6bKmF0/nK HJBMA 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 sets 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) { if (can_is_canxl_dev_mtu(dev->mtu)) return; 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