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Thu, 15 Jan 2026 06:57:12 -0800 (PST) Message-ID: <7e81c093-c578-46ad-b00b-a45da074939a@redhat.com> Date: Thu, 15 Jan 2026 15:57:09 +0100 Precedence: bulk X-Mailing-List: netdev@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH net-next v5 2/4] net: dsa: add tag format for MxL862xx switches To: Daniel Golle , Andrew Lunn , Vladimir Oltean , "David S. Miller" , Eric Dumazet , Jakub Kicinski , Rob Herring , Krzysztof Kozlowski , Conor Dooley , Heiner Kallweit , Russell King , Simon Horman , netdev@vger.kernel.org, devicetree@vger.kernel.org, linux-kernel@vger.kernel.org Cc: Frank Wunderlich , Chad Monroe , Cezary Wilmanski , Avinash Jayaraman , Bing tao Xu , Liang Xu , Juraj Povazanec , "Fanni (Fang-Yi) Chan" , "Benny (Ying-Tsan) Weng" , "Livia M. Rosu" , John Crispin References: <3c44b74b9908c134e52ee9b18c04d26cba51d3d7.1768225363.git.daniel@makrotopia.org> Content-Language: en-US From: Paolo Abeni In-Reply-To: <3c44b74b9908c134e52ee9b18c04d26cba51d3d7.1768225363.git.daniel@makrotopia.org> Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit On 1/12/26 2:51 PM, Daniel Golle wrote: > Add proprietary special tag format for the MaxLinear MXL862xx family of > switches. While using the same Ethertype as MaxLinear's GSW1xx switches, > the actual tag format differs significantly, hence we need a dedicated > tag driver for that. > > Signed-off-by: Daniel Golle > --- > v5: > * remove unused macro definitions > > RFC v4: > * describe fields and variables with comments > * sub-interface is only 5 bits > * harmonize Kconfig symbol name > * maintain alphabetic order in Kconfig > * fix typo s/beginnig/beginning/ > * fix typo s/swtiches/switches/ > * arrange local variables in reverse xmas tree order > > RFC v3: no changes > RFC v2: make sure all tag fields are initialized > > MAINTAINERS | 1 + > include/net/dsa.h | 2 + > net/dsa/Kconfig | 7 +++ > net/dsa/Makefile | 1 + > net/dsa/tag_mxl862xx.c | 116 +++++++++++++++++++++++++++++++++++++++++ > 5 files changed, 127 insertions(+) > create mode 100644 net/dsa/tag_mxl862xx.c > > diff --git a/MAINTAINERS b/MAINTAINERS > index 162859534a77c..686591074b34d 100644 > --- a/MAINTAINERS > +++ b/MAINTAINERS > @@ -15619,6 +15619,7 @@ M: Daniel Golle > L: netdev@vger.kernel.org > S: Maintained > F: Documentation/devicetree/bindings/net/dsa/maxlinear,mxl862xx.yaml > +F: net/dsa/tag_mxl862xx.c > > MCAN DEVICE DRIVER > M: Markus Schneider-Pargmann > diff --git a/include/net/dsa.h b/include/net/dsa.h > index 6b2b5ed64ea4c..1e33242b6d94d 100644 > --- a/include/net/dsa.h > +++ b/include/net/dsa.h > @@ -57,6 +57,7 @@ struct tc_action; > #define DSA_TAG_PROTO_BRCM_LEGACY_FCS_VALUE 29 > #define DSA_TAG_PROTO_YT921X_VALUE 30 > #define DSA_TAG_PROTO_MXL_GSW1XX_VALUE 31 > +#define DSA_TAG_PROTO_MXL862_VALUE 32 > > enum dsa_tag_protocol { > DSA_TAG_PROTO_NONE = DSA_TAG_PROTO_NONE_VALUE, > @@ -91,6 +92,7 @@ enum dsa_tag_protocol { > DSA_TAG_PROTO_VSC73XX_8021Q = DSA_TAG_PROTO_VSC73XX_8021Q_VALUE, > DSA_TAG_PROTO_YT921X = DSA_TAG_PROTO_YT921X_VALUE, > DSA_TAG_PROTO_MXL_GSW1XX = DSA_TAG_PROTO_MXL_GSW1XX_VALUE, > + DSA_TAG_PROTO_MXL862 = DSA_TAG_PROTO_MXL862_VALUE, > }; > > struct dsa_switch; > diff --git a/net/dsa/Kconfig b/net/dsa/Kconfig > index f86b30742122f..efc95759a10e1 100644 > --- a/net/dsa/Kconfig > +++ b/net/dsa/Kconfig > @@ -104,6 +104,13 @@ config NET_DSA_TAG_MTK > Say Y or M if you want to enable support for tagging frames for > Mediatek switches. > > +config NET_DSA_TAG_MXL_862XX > + tristate "Tag driver for MxL862xx switches" > + help > + Say Y or M if you want to enable support for tagging frames for the > + Maxlinear MxL86252 and MxL86282 switches using their native 8-byte > + tagging protocol. > + > config NET_DSA_TAG_MXL_GSW1XX > tristate "Tag driver for MaxLinear GSW1xx switches" > help > diff --git a/net/dsa/Makefile b/net/dsa/Makefile > index 42d173f5a7013..bf7247759a64a 100644 > --- a/net/dsa/Makefile > +++ b/net/dsa/Makefile > @@ -28,6 +28,7 @@ obj-$(CONFIG_NET_DSA_TAG_HELLCREEK) += tag_hellcreek.o > obj-$(CONFIG_NET_DSA_TAG_KSZ) += tag_ksz.o > obj-$(CONFIG_NET_DSA_TAG_LAN9303) += tag_lan9303.o > obj-$(CONFIG_NET_DSA_TAG_MTK) += tag_mtk.o > +obj-$(CONFIG_NET_DSA_TAG_MXL_862XX) += tag_mxl862xx.o > obj-$(CONFIG_NET_DSA_TAG_MXL_GSW1XX) += tag_mxl-gsw1xx.o > obj-$(CONFIG_NET_DSA_TAG_NONE) += tag_none.o > obj-$(CONFIG_NET_DSA_TAG_OCELOT) += tag_ocelot.o > diff --git a/net/dsa/tag_mxl862xx.c b/net/dsa/tag_mxl862xx.c > new file mode 100644 > index 0000000000000..c4d0ea2eb48f9 > --- /dev/null > +++ b/net/dsa/tag_mxl862xx.c > @@ -0,0 +1,116 @@ > +// SPDX-License-Identifier: GPL-2.0-or-later > +/* > + * DSA Special Tag for MaxLinear 862xx switch chips > + * > + * Copyright (C) 2025 Daniel Golle > + * Copyright (C) 2024 MaxLinear Inc. > + */ > + > +#include > +#include > +#include > +#include > +#include "tag.h" > + > +#define MXL862_NAME "mxl862xx" > + > +#define MXL862_HEADER_LEN 8 > + > +/* Word 0 -> EtherType */ > + > +/* Word 2 */ > +#define MXL862_SUBIF_ID GENMASK(4, 0) > + > +/* Word 3 */ > +#define MXL862_IGP_EGP GENMASK(3, 0) > + > +static struct sk_buff *mxl862_tag_xmit(struct sk_buff *skb, > + struct net_device *dev) > +{ > + unsigned int cpu_port, usr_port, sub_interface; > + struct dsa_port *dp = dsa_user_to_port(dev); > + struct dsa_port *cpu_dp = dp->cpu_dp; > + __be16 *mxl862_tag; > + > + /* switch firmware expects ports to be counted starting from 1 */ > + cpu_port = cpu_dp->index + 1; > + usr_port = dp->index + 1; > + > + /* target port sub-interface ID relative to the CPU port */ > + sub_interface = usr_port + 16 - cpu_port; > + > + if (!skb) > + return skb; I think skb can't be NULL here?!? Otherwise it would be better to move the check at the beginning of the function and return NULL directly. > + > + /* provide additional space 'MXL862_HEADER_LEN' bytes */ > + skb_push(skb, MXL862_HEADER_LEN); > + > + /* shift MAC address to the beginning of the enlarged buffer, > + * releasing the space required for DSA tag (between MAC address and > + * Ethertype) > + */ > + dsa_alloc_etype_header(skb, MXL862_HEADER_LEN); > + > + /* special tag ingress */ > + mxl862_tag = dsa_etype_header_pos_tx(skb); > + mxl862_tag[0] = htons(ETH_P_MXLGSW); > + mxl862_tag[1] = 0; > + mxl862_tag[2] = htons(FIELD_PREP(MXL862_SUBIF_ID, sub_interface)); > + mxl862_tag[3] = htons(FIELD_PREP(MXL862_IGP_EGP, cpu_port)); > + > + return skb; > +} > + > +static struct sk_buff *mxl862_tag_rcv(struct sk_buff *skb, > + struct net_device *dev) > +{ > + __be16 *mxl862_tag; > + int port; > + > + if (unlikely(!pskb_may_pull(skb, MXL862_HEADER_LEN))) { > + dev_warn_ratelimited(&dev->dev, "Cannot pull SKB, packet dropped\n"); > + return NULL; > + } > + > + mxl862_tag = dsa_etype_header_pos_rx(skb); > + > + if (unlikely(mxl862_tag[0] != htons(ETH_P_MXLGSW))) { > + dev_warn_ratelimited(&dev->dev, "Invalid special tag marker, packet dropped\n"); > + dev_warn_ratelimited(&dev->dev, "Rx Packet Tag: %8ph\n", > + mxl862_tag); Why breaking the message in 2 strings? a single dev_warn_ratelimited() would be more readable and will generate smaller code. Similar thing below. /P