From: Sergey Ryazanov <ryazanov.s.a@gmail.com>
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.
Add the description for structure member gnss in wwan_port.
CC: Slark Xiao <slark_xiao@163.com>
CC: Muhammad Nuzaihan <zaihan@unrealasia.net>
CC: Qiang Yu <quic_qianyu@quicinc.com>
CC: Manivannan Sadhasivam <manivannan.sadhasivam@linaro.org>
CC: Johan Hovold <johan@kernel.org>
Reported-by: kernel test robot <lkp@intel.com>
Closes: https://lore.kernel.org/oe-kbuild-all/202512312143.W82zclxI-lkp@intel.com/
Suggested-by: Loic Poulain <loic.poulain@oss.qualcomm.com>
Signed-off-by: Sergey Ryazanov <ryazanov.s.a@gmail.com>
---
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 c735b9830e6e..453ff259809c 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 <loic.poulain@linaro.org> */
+/* WWAN Driver Core
+ *
+ * Copyright (c) 2021, Linaro Ltd <loic.poulain@linaro.org>
+ * Copyright (c) 2025, Sergey Ryazanov <ryazanov.s.a@gmail.com>
+ */
#include <linux/bitmap.h>
#include <linux/err.h>
@@ -16,6 +20,7 @@
#include <linux/types.h>
#include <linux/uaccess.h>
#include <linux/termios.h>
+#include <linux/gnss.h>
#include <linux/wwan.h>
#include <net/rtnetlink.h>
#include <uapi/linux/wwan.h>
@@ -71,6 +76,7 @@ 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;
@@ -89,9 +95,16 @@ 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);
@@ -340,6 +353,7 @@ 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,
@@ -488,6 +502,124 @@ 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 mapt 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,
@@ -528,7 +660,11 @@ 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;
@@ -558,7 +694,10 @@ 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);
@@ -569,8 +708,15 @@ 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 */
--
2.25.1On Mon, Jan 5, 2026 at 11:21 AM Slark Xiao <slark_xiao@163.com> wrote:
>
> From: Sergey Ryazanov <ryazanov.s.a@gmail.com>
>
> 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.
>
> Add the description for structure member gnss in wwan_port.
>
> CC: Slark Xiao <slark_xiao@163.com>
> CC: Muhammad Nuzaihan <zaihan@unrealasia.net>
> CC: Qiang Yu <quic_qianyu@quicinc.com>
> CC: Manivannan Sadhasivam <manivannan.sadhasivam@linaro.org>
> CC: Johan Hovold <johan@kernel.org>
>
> Reported-by: kernel test robot <lkp@intel.com>
> Closes: https://lore.kernel.org/oe-kbuild-all/202512312143.W82zclxI-lkp@intel.com/
> Suggested-by: Loic Poulain <loic.poulain@oss.qualcomm.com>
> Signed-off-by: Sergey Ryazanov <ryazanov.s.a@gmail.com>
Reviewed-by: Loic Poulain <loic.poulain@oss.qualcomm.com>
> ---
> 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 c735b9830e6e..453ff259809c 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 <loic.poulain@linaro.org> */
> +/* WWAN Driver Core
> + *
> + * Copyright (c) 2021, Linaro Ltd <loic.poulain@linaro.org>
> + * Copyright (c) 2025, Sergey Ryazanov <ryazanov.s.a@gmail.com>
> + */
>
> #include <linux/bitmap.h>
> #include <linux/err.h>
> @@ -16,6 +20,7 @@
> #include <linux/types.h>
> #include <linux/uaccess.h>
> #include <linux/termios.h>
> +#include <linux/gnss.h>
> #include <linux/wwan.h>
> #include <net/rtnetlink.h>
> #include <uapi/linux/wwan.h>
> @@ -71,6 +76,7 @@ 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;
> @@ -89,9 +95,16 @@ 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);
> @@ -340,6 +353,7 @@ 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,
> @@ -488,6 +502,124 @@ 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 mapt 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,
> @@ -528,7 +660,11 @@ 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;
>
> @@ -558,7 +694,10 @@ 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);
>
> @@ -569,8 +708,15 @@ 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 */
>
> --
> 2.25.1
>
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