[net-next,v4,1/2] net: Add a WWAN subsystem

diff --git a/drivers/net/Kconfig b/drivers/net/Kconfig
index 260f9f4..ec00f92 100644
--- a/drivers/net/Kconfig
+++ b/drivers/net/Kconfig
@@ -500,6 +500,8 @@  source "drivers/net/wan/Kconfig"
 
 source "drivers/net/ieee802154/Kconfig"
 
+source "drivers/net/wwan/Kconfig"
+
 config XEN_NETDEV_FRONTEND
 	tristate "Xen network device frontend driver"
 	depends on XEN
diff --git a/drivers/net/Makefile b/drivers/net/Makefile
index f4990ff..5da6424 100644
--- a/drivers/net/Makefile
+++ b/drivers/net/Makefile
@@ -68,6 +68,7 @@  obj-$(CONFIG_SUNGEM_PHY) += sungem_phy.o
 obj-$(CONFIG_WAN) += wan/
 obj-$(CONFIG_WLAN) += wireless/
 obj-$(CONFIG_IEEE802154) += ieee802154/
+obj-$(CONFIG_WWAN) += wwan/
 
 obj-$(CONFIG_VMXNET3) += vmxnet3/
 obj-$(CONFIG_XEN_NETDEV_FRONTEND) += xen-netfront.o
diff --git a/drivers/net/wwan/Kconfig b/drivers/net/wwan/Kconfig
new file mode 100644
index 0000000..b7d58b7
--- /dev/null
+++ b/drivers/net/wwan/Kconfig
@@ -0,0 +1,19 @@ 
+# SPDX-License-Identifier: GPL-2.0-only
+#
+# Wireless WAN device configuration
+#
+
+menuconfig WWAN
+	bool "Wireless WAN"
+	help
+	  This section contains Wireless WAN driver configurations.
+
+if WWAN
+
+config WWAN_CORE
+	tristate "WWAN Driver Core"
+	help
+	  Say Y here if you want to use the WWAN driver core. This driver
+	  provides a common framework for WWAN drivers.
+
+endif # WWAN
diff --git a/drivers/net/wwan/Makefile b/drivers/net/wwan/Makefile
new file mode 100644
index 0000000..ca8bb5a
--- /dev/null
+++ b/drivers/net/wwan/Makefile
@@ -0,0 +1,8 @@ 
+# SPDX-License-Identifier: GPL-2.0
+#
+# Makefile for the Linux WWAN device drivers.
+#
+
+obj-$(CONFIG_WWAN_CORE) += wwan.o
+wwan-objs += wwan_core.o wwan_port.o
+
diff --git a/drivers/net/wwan/wwan_core.c b/drivers/net/wwan/wwan_core.c
new file mode 100644
index 0000000..46342ab
--- /dev/null
+++ b/drivers/net/wwan/wwan_core.c
@@ -0,0 +1,150 @@ 
+// SPDX-License-Identifier: GPL-2.0-only
+/* Copyright (c) 2021, Linaro Ltd <loic.poulain@linaro.org> */
+
+#include <linux/err.h>
+#include <linux/errno.h>
+#include <linux/init.h>
+#include <linux/fs.h>
+#include <linux/idr.h>
+#include <linux/kernel.h>
+#include <linux/module.h>
+#include <linux/slab.h>
+#include <linux/types.h>
+#include <linux/wwan.h>
+
+#include "wwan_core.h"
+
+static LIST_HEAD(wwan_list);	/* list of registered wwan devices */
+static DEFINE_IDA(wwan_ida);
+static DEFINE_MUTEX(wwan_global_lock);
+struct class *wwan_class;
+
+struct wwan_device *__wwan_find_by_parent(struct device *parent)
+{
+	struct wwan_device *wwandev;
+
+	if (!parent)
+		return NULL;
+
+	list_for_each_entry(wwandev, &wwan_list, list) {
+		if (wwandev->dev.parent == parent)
+			return wwandev;
+	}
+
+	return NULL;
+}
+
+static void wwan_dev_release(struct device *dev)
+{
+	struct wwan_device *wwandev = to_wwan_dev(dev);
+
+	kfree(wwandev);
+}
+
+static const struct device_type wwan_type = {
+	.name    = "wwan",
+	.release = wwan_dev_release,
+};
+
+struct wwan_device *wwan_create_dev(struct device *parent)
+{
+	struct wwan_device *wwandev;
+	int err, id;
+
+	mutex_lock(&wwan_global_lock);
+
+	wwandev = __wwan_find_by_parent(parent);
+	if (wwandev) {
+		get_device(&wwandev->dev);
+		wwandev->usage++;
+		goto done_unlock;
+	}
+
+	id = ida_alloc(&wwan_ida, GFP_KERNEL);
+	if (id < 0)
+		goto done_unlock;
+
+	wwandev = kzalloc(sizeof(*wwandev), GFP_KERNEL);
+	if (!wwandev) {
+		ida_free(&wwan_ida, id);
+		goto done_unlock;
+	}
+
+	wwandev->dev.parent = parent;
+	wwandev->dev.class = wwan_class;
+	wwandev->dev.type = &wwan_type;
+	wwandev->id = id;
+	dev_set_name(&wwandev->dev, "wwan%d", wwandev->id);
+	wwandev->usage = 1;
+	INIT_LIST_HEAD(&wwandev->ports);
+
+	err = device_register(&wwandev->dev);
+	if (err) {
+		put_device(&wwandev->dev);
+		ida_free(&wwan_ida, id);
+		wwandev = NULL;
+		goto done_unlock;
+	}
+
+	list_add_tail(&wwandev->list, &wwan_list);
+
+done_unlock:
+	mutex_unlock(&wwan_global_lock);
+
+	return wwandev;
+}
+EXPORT_SYMBOL_GPL(wwan_create_dev);
+
+void wwan_destroy_dev(struct wwan_device *wwandev)
+{
+	mutex_lock(&wwan_global_lock);
+	wwandev->usage--;
+
+	if (wwandev->usage)
+		goto done_unlock;
+
+	/* Someone destroyed the wwan device without removing ports */
+	WARN_ON(!list_empty(&wwandev->ports));
+
+	list_del(&wwandev->list);
+	device_unregister(&wwandev->dev);
+	ida_free(&wwan_ida, wwandev->id);
+	put_device(&wwandev->dev);
+
+done_unlock:
+	mutex_unlock(&wwan_global_lock);
+}
+EXPORT_SYMBOL_GPL(wwan_destroy_dev);
+
+static int __init wwan_init(void)
+{
+	int err;
+
+	wwan_class = class_create(THIS_MODULE, "wwan");
+	if (IS_ERR(wwan_class))
+		return PTR_ERR(wwan_class);
+
+	err = wwan_port_init();
+	if (err)
+		goto err_class_destroy;
+
+	return 0;
+
+err_class_destroy:
+	class_destroy(wwan_class);
+	return err;
+}
+
+static void __exit wwan_exit(void)
+{
+	wwan_port_deinit();
+	class_destroy(wwan_class);
+}
+
+//subsys_initcall(wwan_init);
+module_init(wwan_init);
+module_exit(wwan_exit);
+
+MODULE_AUTHOR("Loic Poulain <loic.poulain@linaro.org>");
+MODULE_DESCRIPTION("WWAN core");
+MODULE_LICENSE("GPL v2");
diff --git a/drivers/net/wwan/wwan_core.h b/drivers/net/wwan/wwan_core.h
new file mode 100644
index 0000000..21d187a
--- /dev/null
+++ b/drivers/net/wwan/wwan_core.h
@@ -0,0 +1,20 @@ 
+/* SPDX-License-Identifier: GPL-2.0-only */
+/* Copyright (c) 2021, Linaro Ltd <loic.poulain@linaro.org> */
+
+#ifndef __WWAN_CORE_H
+#define __WWAN_CORE_H
+
+#include <linux/device.h>
+#include <linux/wwan.h>
+
+#define to_wwan_dev(d) container_of(d, struct wwan_device, dev)
+
+struct wwan_device *wwan_create_dev(struct device *parent);
+void wwan_destroy_dev(struct wwan_device *wwandev);
+
+int wwan_port_init(void);
+void wwan_port_deinit(void);
+
+extern struct class *wwan_class;
+
+#endif /* WWAN_CORE_H */
diff --git a/drivers/net/wwan/wwan_port.c b/drivers/net/wwan/wwan_port.c
new file mode 100644
index 0000000..625d616
--- /dev/null
+++ b/drivers/net/wwan/wwan_port.c
@@ -0,0 +1,136 @@ 
+// SPDX-License-Identifier: GPL-2.0-only
+/* Copyright (c) 2021, Linaro Ltd <loic.poulain@linaro.org> */
+
+#include <linux/err.h>
+#include <linux/errno.h>
+#include <linux/fs.h>
+#include <linux/idr.h>
+#include <linux/kernel.h>
+#include <linux/module.h>
+#include <linux/wwan.h>
+
+#include "wwan_core.h"
+
+#define WWAN_MAX_MINORS 128
+
+static int wwan_major;
+static DEFINE_IDR(wwan_port_idr);
+static DEFINE_MUTEX(wwan_port_idr_lock);
+
+static const char * const wwan_port_type_str[] = {
+	"AT",
+	"MBIM",
+	"QMI",
+	"QCDM",
+	"FIREHOSE"
+};
+
+int wwan_add_port(struct wwan_port *port)
+{
+	struct wwan_device *wwandev = port->wwandev;
+	struct device *dev;
+	int minor, err;
+
+	if (port->type >= WWAN_PORT_MAX || !port->fops || !wwandev)
+		return -EINVAL;
+
+	mutex_lock(&wwan_port_idr_lock);
+	minor = idr_alloc(&wwan_port_idr, port, 0, WWAN_MAX_MINORS, GFP_KERNEL);
+	mutex_unlock(&wwan_port_idr_lock);
+
+	if (minor < 0)
+		return minor;
+
+	mutex_lock(&wwandev->lock);
+
+	dev = device_create(wwan_class, &wwandev->dev,
+			    MKDEV(wwan_major, minor), port,
+			    "wwan%dp%u%s", wwandev->id, wwandev->port_idx,
+			    wwan_port_type_str[port->type]);
+	if (IS_ERR(dev)) {
+		err = PTR_ERR(dev);
+		mutex_unlock(&wwandev->lock);
+		goto error_free_idr;
+	}
+
+	port->id = wwandev->port_idx++;
+	port->minor = minor;
+
+	list_add(&port->list, &wwandev->ports);
+
+	mutex_unlock(&port->wwandev->lock);
+
+	return 0;
+
+error_free_idr:
+	mutex_lock(&wwan_port_idr_lock);
+	idr_remove(&wwan_port_idr, minor);
+	mutex_unlock(&wwan_port_idr_lock);
+
+	return err;
+}
+EXPORT_SYMBOL_GPL(wwan_add_port);
+
+void wwan_remove_port(struct wwan_port *port)
+{
+	struct wwan_device *wwandev = port->wwandev;
+
+	WARN_ON(!wwandev);
+
+	mutex_lock(&wwandev->lock);
+	device_destroy(wwan_class, MKDEV(wwan_major, port->minor));
+	list_del(&port->list);
+	mutex_unlock(&wwandev->lock);
+
+	mutex_lock(&wwan_port_idr_lock);
+	idr_remove(&wwan_port_idr, port->minor);
+	mutex_unlock(&wwan_port_idr_lock);
+}
+EXPORT_SYMBOL_GPL(wwan_remove_port);
+
+static int wwan_port_open(struct inode *inode, struct file *file)
+{
+	const struct file_operations *new_fops;
+	unsigned int minor = iminor(inode);
+	struct wwan_port *port;
+	int err = 0;
+
+	mutex_lock(&wwan_port_idr_lock);
+	port = idr_find(&wwan_port_idr, minor);
+	if (!port) {
+		mutex_unlock(&wwan_port_idr_lock);
+		return -ENODEV;
+	}
+	mutex_unlock(&wwan_port_idr_lock);
+
+	file->private_data = port->private_data ? port->private_data : port;
+	stream_open(inode, file);
+
+	new_fops = fops_get(port->fops);
+	replace_fops(file, new_fops);
+	if (file->f_op->open)
+		err = file->f_op->open(inode, file);
+
+	return err;
+}
+
+static const struct file_operations wwan_port_fops = {
+	.owner	= THIS_MODULE,
+	.open	= wwan_port_open,
+	.llseek = noop_llseek,
+};
+
+int wwan_port_init(void)
+{
+	wwan_major = register_chrdev(0, "wwanport", &wwan_port_fops);
+	if (wwan_major < 0)
+		return wwan_major;
+
+	return 0;
+}
+
+void wwan_port_deinit(void)
+{
+	unregister_chrdev(wwan_major, "wwanport");
+	idr_destroy(&wwan_port_idr);
+}
diff --git a/include/linux/wwan.h b/include/linux/wwan.h
new file mode 100644
index 0000000..6caca5c
--- /dev/null
+++ b/include/linux/wwan.h
@@ -0,0 +1,121 @@ 
+/* SPDX-License-Identifier: GPL-2.0-only */
+/* Copyright (c) 2021, Linaro Ltd <loic.poulain@linaro.org> */
+
+#ifndef __WWAN_H
+#define __WWAN_H
+
+#include <linux/device.h>
+#include <linux/kernel.h>
+
+/**
+ * struct wwan_device - The structure that defines a WWAN device
+ *
+ * @id:		WWAN device unique ID.
+ * @usage:	WWAN device usage counter.
+ * @dev:	underlying device.
+ * @list:	list to chain WWAN devices.
+ * @ports:	list of attached wwan_port.
+ * @port_idx:	port index counter.
+ * @lock:	mutex protecting members of this structure.
+ */
+struct wwan_device {
+	int id;
+	unsigned int usage;
+
+	struct device dev;
+	struct list_head list;
+
+	struct list_head ports;
+	unsigned int port_idx;
+
+	struct mutex lock;
+};
+
+/**
+ * enum wwan_port_type - WWAN port types
+ * @WWAN_PORT_AT:	AT commands.
+ * @WWAN_PORT_MBIM:	Mobile Broadband Interface Model control.
+ * @WWAN_PORT_QMI:	Qcom modem/MSM interface for modem control.
+ * @WWAN_PORT_QCDM:	Qcom Modem diagnostic interface.
+ * @WWAN_PORT_FIREHOSE: XML based command protocol.
+ * @WWAN_PORT_MAX
+ */
+enum wwan_port_type {
+	WWAN_PORT_AT,
+	WWAN_PORT_MBIM,
+	WWAN_PORT_QMI,
+	WWAN_PORT_QCDM,
+	WWAN_PORT_FIREHOSE,
+	WWAN_PORT_MAX,
+};
+
+/**
+ * struct wwan_port - The structure that defines a WWAN port
+ *
+ * @wwandev:		WWAN device this port belongs to.
+ * @fops:		Port file operations.
+ * @private_data:	underlying device.
+ * @type:		port type.
+ * @id:			port allocated ID.
+ * @minor:		port allocated minor ID for cdev.
+ * @list:		list to chain WWAN ports.
+ */
+struct wwan_port {
+	struct wwan_device *wwandev;
+	const struct file_operations *fops;
+	void *private_data;
+	enum wwan_port_type type;
+
+	/* private */
+	unsigned int id;
+	int minor;
+	struct list_head list;
+};
+
+#define to_wwan_dev(d) container_of(d, struct wwan_device, dev)
+
+/**
+ * wwan_create_dev - Create a new WWAN device
+ * @parent: parent device of the WWAN device
+ *
+ * If parent is not NULL, WWAN core ensures that only one WWAN device is
+ * allocated for a given parent. If a WWAN device with the specified parent
+ * already exists, a reference is taken and the WWAN device is returned.
+ *
+ * This function must be balanced with a call to wwan_destroy_dev().
+ *
+ * Returns pointer to the wwan_device or NULL.
+ */
+struct wwan_device *wwan_create_dev(struct device *parent);
+
+/**
+ * wwan_create_dev - Destroy a WWAN device
+ * @wwandev: wwan_device to destroy
+ *
+ * This releases a previoulsy created WWAN device.
+ */
+void wwan_destroy_dev(struct wwan_device *wwandev);
+
+/**
+ * wwan_add_port - Add a new WWAN port
+ * @port: WWAN port to add
+ *
+ * Prior calling this function, caller must allocate and fill the wwan_port
+ * with wwandev, fops, and type fields. A port is automatically exposed to
+ * user as character device, and provided file operations will be used.
+ *
+ * This function must be balanced with a call to wwan_remove_port().
+ *
+ * Returns zero on success or a negative error code.
+ */
+int wwan_add_port(struct wwan_port *port);
+
+/**
+ * wwan_remove_port - Remove a WWAN port
+ * @port: WWAN port to remove
+ *
+ * Remove a previously added port.
+ */
+void wwan_remove_port(struct wwan_port *port);
+
+#endif /* __WWAN_H */