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Miller" , Jakub Kicinski , Paolo Abeni , netdev@vger.kernel.org, Slark Xiao , Muhammad Nuzaihan , Qiang Yu , Manivannan Sadhasivam , Johan Hovold Subject: [RFC PATCH v5 5/7] net: wwan: add NMEA port support Date: Fri, 9 Jan 2026 03:09:07 +0200 Message-ID: <20260109010909.4216-6-ryazanov.s.a@gmail.com> X-Mailer: git-send-email 2.52.0 In-Reply-To: <20260109010909.4216-1-ryazanov.s.a@gmail.com> References: <20260109010909.4216-1-ryazanov.s.a@gmail.com> Precedence: bulk X-Mailing-List: netdev@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit Many WWAN modems come with embedded GNSS receiver inside and have a dedicated port to output geopositioning data. On the one hand, the GNSS receiver has little in common with WWAN modem and just shares a host interface and should be exported using the GNSS subsystem. On the other hand, GNSS receiver is not automatically activated and needs a generic WWAN control port (AT, MBIM, etc.) to be turned on. And a user space software needs extra information to find the control port. Introduce the new type of WWAN port - NMEA. When driver asks to register a NMEA port, the core allocates common parent WWAN device as usual, but exports the NMEA port via the GNSS subsystem and acts as a proxy between the device driver and the GNSS subsystem. >From the WWAN device driver perspective, a NMEA port is registered as a regular WWAN port without any difference. And the driver interacts only with the WWAN core. From the user space perspective, the NMEA port is a GNSS device which parent can be used to enumerate and select the proper control port for the GNSS receiver management. CC: Slark Xiao CC: Muhammad Nuzaihan CC: Qiang Yu CC: Manivannan Sadhasivam CC: Johan Hovold Suggested-by: Loic Poulain Signed-off-by: Sergey Ryazanov Reviewed-by: Loic Poulain --- Changes: * RFCv2->RFCv5: became 5/7 (was 4/6); add missed gnss field documentation --- drivers/net/wwan/Kconfig | 1 + drivers/net/wwan/wwan_core.c | 156 +++++++++++++++++++++++++++++++++-- include/linux/wwan.h | 2 + 3 files changed, 154 insertions(+), 5 deletions(-) diff --git a/drivers/net/wwan/Kconfig b/drivers/net/wwan/Kconfig index 410b0245114e..88df55d78d90 100644 --- a/drivers/net/wwan/Kconfig +++ b/drivers/net/wwan/Kconfig @@ -7,6 +7,7 @@ menu "Wireless WAN" config WWAN tristate "WWAN Driver Core" + depends on GNSS || GNSS = n help Say Y here if you want to use the WWAN driver core. This driver provides a common framework for WWAN drivers. diff --git a/drivers/net/wwan/wwan_core.c b/drivers/net/wwan/wwan_core.c index 798b7ef0549e..2544caa1ff91 100644 --- a/drivers/net/wwan/wwan_core.c +++ b/drivers/net/wwan/wwan_core.c @@ -1,5 +1,9 @@ // SPDX-License-Identifier: GPL-2.0-only -/* Copyright (c) 2021, Linaro Ltd */ +/* WWAN Driver Core + * + * Copyright (c) 2021, Linaro Ltd + * Copyright (c) 2025, Sergey Ryazanov + */ #include #include @@ -16,6 +20,7 @@ #include #include #include +#include #include #include #include @@ -75,6 +80,7 @@ struct wwan_device { * @headroom_len: SKB reserved headroom size * @frag_len: Length to fragment packet * @at_data: AT port specific data + * @gnss: Pointer to GNSS device associated with this port */ struct wwan_port { enum wwan_port_type type; @@ -93,9 +99,16 @@ struct wwan_port { struct ktermios termios; int mdmbits; } at_data; + struct gnss_device *gnss; }; }; +static int wwan_port_op_start(struct wwan_port *port); +static void wwan_port_op_stop(struct wwan_port *port); +static int wwan_port_op_tx(struct wwan_port *port, struct sk_buff *skb, + bool nonblock); +static int wwan_wait_tx(struct wwan_port *port, bool nonblock); + static ssize_t index_show(struct device *dev, struct device_attribute *attr, char *buf) { struct wwan_device *wwan = to_wwan_dev(dev); @@ -339,6 +352,7 @@ static const struct { .name = "MIPC", .devsuf = "mipc", }, + /* WWAN_PORT_NMEA is exported via the GNSS subsystem */ }; static ssize_t type_show(struct device *dev, struct device_attribute *attr, @@ -489,6 +503,124 @@ static void wwan_port_unregister_wwan(struct wwan_port *port) device_del(&port->dev); } +#if IS_ENABLED(CONFIG_GNSS) +static int wwan_gnss_open(struct gnss_device *gdev) +{ + return wwan_port_op_start(gnss_get_drvdata(gdev)); +} + +static void wwan_gnss_close(struct gnss_device *gdev) +{ + wwan_port_op_stop(gnss_get_drvdata(gdev)); +} + +static int wwan_gnss_write(struct gnss_device *gdev, const unsigned char *buf, + size_t count) +{ + struct wwan_port *port = gnss_get_drvdata(gdev); + struct sk_buff *skb, *head = NULL, *tail = NULL; + size_t frag_len, remain = count; + int ret; + + ret = wwan_wait_tx(port, false); + if (ret) + return ret; + + do { + frag_len = min(remain, port->frag_len); + skb = alloc_skb(frag_len + port->headroom_len, GFP_KERNEL); + if (!skb) { + ret = -ENOMEM; + goto freeskb; + } + skb_reserve(skb, port->headroom_len); + memcpy(skb_put(skb, frag_len), buf + count - remain, frag_len); + + if (!head) { + head = skb; + } else { + if (!tail) + skb_shinfo(head)->frag_list = skb; + else + tail->next = skb; + + tail = skb; + head->data_len += skb->len; + head->len += skb->len; + head->truesize += skb->truesize; + } + } while (remain -= frag_len); + + ret = wwan_port_op_tx(port, head, false); + if (!ret) + return count; + +freeskb: + kfree_skb(head); + return ret; +} + +static struct gnss_operations wwan_gnss_ops = { + .open = wwan_gnss_open, + .close = wwan_gnss_close, + .write_raw = wwan_gnss_write, +}; + +/* GNSS port specific device registration */ +static int wwan_port_register_gnss(struct wwan_port *port) +{ + struct wwan_device *wwandev = to_wwan_dev(port->dev.parent); + struct gnss_device *gdev; + int err; + + gdev = gnss_allocate_device(&wwandev->dev); + if (!gdev) + return -ENOMEM; + + /* NB: for now we support only NMEA WWAN port type, so hardcode + * the GNSS port type. If more GNSS WWAN port types will be added, + * then we should dynamically map WWAN port type to GNSS type. + */ + gdev->type = GNSS_TYPE_NMEA; + gdev->ops = &wwan_gnss_ops; + gnss_set_drvdata(gdev, port); + + port->gnss = gdev; + + err = gnss_register_device(gdev); + if (err) { + gnss_put_device(gdev); + return err; + } + + dev_info(&wwandev->dev, "port %s attached\n", dev_name(&gdev->dev)); + + return 0; +} + +/* GNSS port specific device unregistration */ +static void wwan_port_unregister_gnss(struct wwan_port *port) +{ + struct wwan_device *wwandev = to_wwan_dev(port->dev.parent); + struct gnss_device *gdev = port->gnss; + + dev_info(&wwandev->dev, "port %s disconnected\n", dev_name(&gdev->dev)); + + gnss_deregister_device(gdev); + gnss_put_device(gdev); +} +#else +static inline int wwan_port_register_gnss(struct wwan_port *port) +{ + return -EOPNOTSUPP; +} + +static inline void wwan_port_unregister_gnss(struct wwan_port *port) +{ + WARN_ON(1); /* This handler cannot be called */ +} +#endif + struct wwan_port *wwan_create_port(struct device *parent, enum wwan_port_type type, const struct wwan_port_ops *ops, @@ -529,7 +661,11 @@ struct wwan_port *wwan_create_port(struct device *parent, dev_set_drvdata(&port->dev, drvdata); device_initialize(&port->dev); - err = wwan_port_register_wwan(port); + if (port->type == WWAN_PORT_NMEA) + err = wwan_port_register_gnss(port); + else + err = wwan_port_register_wwan(port); + if (err) goto error_put_device; @@ -559,7 +695,10 @@ void wwan_remove_port(struct wwan_port *port) wake_up_interruptible(&port->waitqueue); skb_queue_purge(&port->rxq); - wwan_port_unregister_wwan(port); + if (port->type == WWAN_PORT_NMEA) + wwan_port_unregister_gnss(port); + else + wwan_port_unregister_wwan(port); put_device(&port->dev); @@ -570,8 +709,15 @@ EXPORT_SYMBOL_GPL(wwan_remove_port); void wwan_port_rx(struct wwan_port *port, struct sk_buff *skb) { - skb_queue_tail(&port->rxq, skb); - wake_up_interruptible(&port->waitqueue); + if (port->type == WWAN_PORT_NMEA) { +#if IS_ENABLED(CONFIG_GNSS) + gnss_insert_raw(port->gnss, skb->data, skb->len); +#endif + consume_skb(skb); + } else { + skb_queue_tail(&port->rxq, skb); + wake_up_interruptible(&port->waitqueue); + } } EXPORT_SYMBOL_GPL(wwan_port_rx); diff --git a/include/linux/wwan.h b/include/linux/wwan.h index a4d6cc0c9f68..1e0e2cb53579 100644 --- a/include/linux/wwan.h +++ b/include/linux/wwan.h @@ -19,6 +19,7 @@ * @WWAN_PORT_FASTBOOT: Fastboot protocol control * @WWAN_PORT_ADB: ADB protocol control * @WWAN_PORT_MIPC: MTK MIPC diagnostic interface + * @WWAN_PORT_NMEA: embedded GNSS receiver with NMEA output * * @WWAN_PORT_MAX: Highest supported port types * @WWAN_PORT_UNKNOWN: Special value to indicate an unknown port type @@ -34,6 +35,7 @@ enum wwan_port_type { WWAN_PORT_FASTBOOT, WWAN_PORT_ADB, WWAN_PORT_MIPC, + WWAN_PORT_NMEA, /* Add new port types above this line */ -- 2.52.0