From patchwork Tue Apr 9 10:58:46 2024 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Maxime Chevallier X-Patchwork-Id: 13622276 X-Patchwork-Delegate: kuba@kernel.org Received: from relay6-d.mail.gandi.net (relay6-d.mail.gandi.net [217.70.183.198]) (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 1E51212E1F7; Tue, 9 Apr 2024 10:59:04 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=217.70.183.198 ARC-Seal: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1712660347; cv=none; b=A1sDIiIY/UEBvA2UUK8T66e64b9CV1Yp5ibwu6nDPgqxvX8tlkGaSSK2IweyQaR1wlizkjvt1KkPduYWx4R0K6NP1TQ8/RuQDGTZh1/9cLvdyQk7OVsnAkWS+DLnqV5zy8OfbvSCoPXeP+AIVftu0PG8HEToZBcth/Z7bAp48qc= ARC-Message-Signature: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1712660347; c=relaxed/simple; bh=Q2eayK5FjhqiLuaHkjorwaRgB+ThC/e6b07FRlLuAr4=; h=From:To:Cc:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version; b=DH2ttu+7RzE4Y6Vm8sWoj4rwedZJKsk3XW1oAWk4HIpWnWVjD/wSc5nk0vwQVZGWC8q0wU+lJieXvQXm6ZSHS5G9AOOC26FpvXmrp3s4bLxbQw7dmeVRWTnSZbhtFTE3BKek4wlwn7mDeroIbiVAtzQCJrCSpXZJ6gkQw8Hz1a4= ARC-Authentication-Results: i=1; smtp.subspace.kernel.org; dmarc=pass (p=reject dis=none) header.from=bootlin.com; spf=pass smtp.mailfrom=bootlin.com; dkim=pass (2048-bit key) header.d=bootlin.com header.i=@bootlin.com header.b=N7OFXTgv; arc=none smtp.client-ip=217.70.183.198 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=reject dis=none) header.from=bootlin.com Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=bootlin.com Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=bootlin.com header.i=@bootlin.com header.b="N7OFXTgv" Received: by mail.gandi.net (Postfix) with ESMTPSA id 91D07C000F; Tue, 9 Apr 2024 10:59:02 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=bootlin.com; s=gm1; t=1712660343; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references; bh=5hzdD3iQ2ioDWjARjRtQGGxrXv51LODauFhkOMOYviE=; b=N7OFXTgvxfIQwliv+KYJ2PfmEBtcCZ2Joj9r7yAPLi0xmaiXSlw1HF+ASMdEO7ZtFCkFTX OqUkxksATDwmWKPKecqzMwQ/W4noVtFdJapa97VYSNL9ebFi1LAx+VnqxpMW747R6Dq528 KsNOjzuWCE52tXEnpWyd2Y2etsYG28EIugpf4/v48Fxz4HzMAb1yVnbK6qMtgwZ/TsMwbc ui57Wn5C96J3SpA/OeY4XMNN96kCJs8jHpf2g2n58osDJZZ5preZ+aNRKiYyCYGokDhGtG xCMUw9q+egu9JZqtghIX3qOetYoIJrbEdyzH+XRkAJ8JtZ1P0qvdv1eCf1fzpg== From: Maxime Chevallier To: davem@davemloft.net Cc: Maxime Chevallier , netdev@vger.kernel.org, linux-kernel@vger.kernel.org, thomas.petazzoni@bootlin.com, Andrew Lunn , Jakub Kicinski , Eric Dumazet , Paolo Abeni , Russell King , linux-arm-kernel@lists.infradead.org, Christophe Leroy , Herve Codina , Florian Fainelli , Heiner Kallweit , Vladimir Oltean , =?utf-8?q?K=C3=B6ry_Maincent?= , Jesse Brandeburg , Jonathan Corbet , =?utf-8?q?Marek_Beh=C3=BAn?= , Piergiorgio Beruto , Oleksij Rempel , =?utf-8?q?Nicol=C3=B2_Veronese?= , Simon Horman , mwojtas@chromium.org Subject: [PATCH net-next 8/8] Documentation: networking: document phy_link_topology Date: Tue, 9 Apr 2024 12:58:46 +0200 Message-ID: <20240409105847.465298-9-maxime.chevallier@bootlin.com> X-Mailer: git-send-email 2.44.0 In-Reply-To: <20240409105847.465298-1-maxime.chevallier@bootlin.com> References: <20240409105847.465298-1-maxime.chevallier@bootlin.com> Precedence: bulk X-Mailing-List: netdev@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 X-GND-Sasl: maxime.chevallier@bootlin.com X-Patchwork-Delegate: kuba@kernel.org The newly introduced phy_link_topology tracks all ethernet PHYs that are attached to a netdevice. Document the base principle, internal and external APIs. As the phy_link_topology is expected to be extended, this documentation will hold any further improvements and additions made relative to topology handling. Signed-off-by: Maxime Chevallier Reviewed-by: Andrew Lunn --- Documentation/networking/ethtool-netlink.rst | 3 + Documentation/networking/index.rst | 1 + .../networking/phy-link-topology.rst | 120 ++++++++++++++++++ 3 files changed, 124 insertions(+) create mode 100644 Documentation/networking/phy-link-topology.rst diff --git a/Documentation/networking/ethtool-netlink.rst b/Documentation/networking/ethtool-netlink.rst index b89a3d562018..1ae3bfd805ce 100644 --- a/Documentation/networking/ethtool-netlink.rst +++ b/Documentation/networking/ethtool-netlink.rst @@ -2027,10 +2027,13 @@ Retrieve information about a given Ethernet PHY sitting on the link. The DO operation returns all available information about dev->phydev. User can also specify a PHY_INDEX, in which case the DO request returns information about that specific PHY. + As there can be more than one PHY, the DUMP operation can be used to list the PHYs present on a given interface, by passing an interface index or name in the dump request. +For more information, refer to :ref:`Documentation/networking/phy-link-topology.rst` + Request contents: ==================================== ====== ========================== diff --git a/Documentation/networking/index.rst b/Documentation/networking/index.rst index 473d72c36d61..c29bc5179d8a 100644 --- a/Documentation/networking/index.rst +++ b/Documentation/networking/index.rst @@ -89,6 +89,7 @@ Contents: operstates packet_mmap phonet + phy-link-topology pktgen plip ppp_generic diff --git a/Documentation/networking/phy-link-topology.rst b/Documentation/networking/phy-link-topology.rst new file mode 100644 index 000000000000..1f021419ae8c --- /dev/null +++ b/Documentation/networking/phy-link-topology.rst @@ -0,0 +1,120 @@ +.. SPDX-License-Identifier: GPL-2.0 + +================= +PHY link topology +================= + +Overview +======== + +The PHY link topology representation in the networking stack aims at representing +the hardware layout for any given Ethernet link. + +An Ethernet interface from userspace's point of view is nothing but a +:c:type:`struct net_device `, which exposes configuration options +through the legacy ioctls and the ethtool netlink commands. The base assumption +when designing these configuration APIs were that the link looks something like :: + + +-----------------------+ +----------+ +--------------+ + | Ethernet Controller / | | Ethernet | | Connector / | + | MAC | ------ | PHY | ---- | Port | ---... to LP + +-----------------------+ +----------+ +--------------+ + struct net_device struct phy_device + +Commands that needs to configure the PHY will go through the net_device.phydev +field to reach the PHY and perform the relevant configuration. + +This assumption falls apart in more complex topologies that can arise when, +for example, using SFP transceivers (although that's not the only specific case). + +Here, we have 2 basic scenarios. Either the MAC is able to output a serialized +interface, that can directly be fed to an SFP cage, such as SGMII, 1000BaseX, +10GBaseR, etc. + +The link topology then looks like this (when an SFP module is inserted) :: + + +-----+ SGMII +------------+ + | MAC | ------- | SFP Module | + +-----+ +------------+ + +Knowing that some modules embed a PHY, the actual link is more like :: + + +-----+ SGMII +--------------+ + | MAC | -------- | PHY (on SFP) | + +-----+ +--------------+ + +In this case, the SFP PHY is handled by phylib, and registered by phylink through +its SFP upstream ops. + +Now some Ethernet controllers aren't able to output a serialized interface, so +we can't directly connect them to an SFP cage. However, some PHYs can be used +as media-converters, to translate the non-serialized MAC MII interface to a +serialized MII interface fed to the SFP :: + + +-----+ RGMII +-----------------------+ SGMII +--------------+ + | MAC | ------- | PHY (media converter) | ------- | PHY (on SFP) | + +-----+ +-----------------------+ +--------------+ + +This is where the model of having a single net_device.phydev pointer shows its +limitations, as we now have 2 PHYs on the link. + +The phy_link topology framework aims at providing a way to keep track of every +PHY on the link, for use by both kernel drivers and subsystems, but also to +report the topology to userspace, allowing to target individual PHYs in configuration +commands. + +API +=== + +The :c:type:`struct phy_link_topology ` is a per-netdevice +resource, that gets initialized at netdevice creation. Once it's initialized, +it is then possible to register PHYs to the topology through : + +:c:func:`phy_link_topo_add_phy` + +Besides registering the PHY to the topology, this call will also assign a unique +index to the PHY, which can then be reported to userspace to refer to this PHY +(akin to the ifindex). This index is a u32, ranging from 1 to U32_MAX. The value +0 is reserved to indicate the PHY doesn't belong to any topology yet. + +The PHY can then be removed from the topology through + +:c:func:`phy_link_topo_del_phy` + +These function are already hooked into the phylib subsystem, so all PHYs that +are linked to a net_device through :c:func:`phy_attach_direct` will automatically +join the netdev's topology. + +PHYs that are on a SFP module will also be automatically registered IF the SFP +upstream is phylink (so, no media-converter). + +PHY drivers that can be used as SFP upstream need to call :c:func:`phy_sfp_attach_phy` +and :c:func:`phy_sfp_detach_phy`, which can be used as a +.attach_phy / .detach_phy implementation for the +:c:type:`struct sfp_upstream_ops `. + +UAPI +==== + +There exist a set of netlink commands to query the link topology from userspace, +see ``Documentation/networking/ethtool-netlink.rst``. + +The whole point of having a topology representation is to assign the phyindex +field in :c:type:`struct phy_device `. This index is reported to +userspace using the ``ETHTOOL_MSG_PHY_GET`` ethtnl command. Performing a DUMP operation +will result in all PHYs from all net_device being listed. The DUMP command +accepts either a ``ETHTOOL_A_HEADER_DEV_INDEX`` or ``ETHTOOL_A_HEADER_DEV_NAME`` +to be passed in the request to filter the DUMP to a single net_device. + +The retrieved index can then be passed as a request parameter using the +``ETHTOOL_A_HEADER_PHY_INDEX`` field in the following ethnl commands : + +* ``ETHTOOL_MSG_STRSET_GET`` to get the stats string set from a given PHY +* ``ETHTOOL_MSG_CABLE_TEST_ACT`` and ``ETHTOOL_MSG_CABLE_TEST_ACT``, to perform + cable testing on a given PHY on the link (most likely the outermost PHY) +* ``ETHTOOL_MSG_PSE_SET`` and ``ETHTOOL_MSG_PSE_GET`` for PHY-controlled PoE and PSE settings +* ``ETHTOOL_MSG_PLCA_GET_CFG``, ``ETHTOOL_MSG_PLCA_SET_CFG`` and ``ETHTOOL_MSG_PLCA_GET_STATUS`` + to set the PLCA (Physical Layer Collision Avoidance) parameters + +Note that the PHY index can be passed to other requests, which will silently +ignore it if present and irrelevant.