[net-next,v7,1/2] net: Add a WWAN subsystem

diff --git a/drivers/net/Kconfig b/drivers/net/Kconfig
index 5895905..74dc8e24 100644
--- a/drivers/net/Kconfig
+++ b/drivers/net/Kconfig
@@ -502,6 +502,8 @@  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 040e20b..7ffd2d0 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..545fe54
--- /dev/null
+++ b/drivers/net/wwan/Kconfig
@@ -0,0 +1,22 @@ 
+# 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.
+
+	  To compile this driver as a module, choose M here: the module will be
+	  called wwan.
+
+endif # WWAN
diff --git a/drivers/net/wwan/Makefile b/drivers/net/wwan/Makefile
new file mode 100644
index 0000000..934590b
--- /dev/null
+++ b/drivers/net/wwan/Makefile
@@ -0,0 +1,7 @@ 
+# SPDX-License-Identifier: GPL-2.0
+#
+# Makefile for the Linux WWAN device drivers.
+#
+
+obj-$(CONFIG_WWAN_CORE) += wwan.o
+wwan-objs += wwan_core.o
diff --git a/drivers/net/wwan/wwan_core.c b/drivers/net/wwan/wwan_core.c
new file mode 100644
index 0000000..7d9e2643
--- /dev/null
+++ b/drivers/net/wwan/wwan_core.c
@@ -0,0 +1,317 @@ 
+// 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/init.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>
+
+#define WWAN_MAX_MINORS 256 /* Allow the whole available cdev range of minors */
+
+static DEFINE_MUTEX(wwan_register_lock); /* WWAN device create|remove lock */
+static DEFINE_IDA(minors); /* minors for WWAN port chardevs */
+static DEFINE_IDA(wwan_dev_ids); /* for unique WWAN device IDs */
+static struct class *wwan_class;
+static int wwan_major;
+
+#define to_wwan_dev(d) container_of(d, struct wwan_device, dev)
+#define to_wwan_port(d) container_of(d, struct wwan_port, dev)
+
+/**
+ * struct wwan_device - The structure that defines a WWAN device
+ *
+ * @id: WWAN device unique ID.
+ * @dev: Underlying device.
+ * @port_id: Current available port ID to pick.
+ */
+struct wwan_device {
+	unsigned int id;
+	struct device dev;
+	atomic_t port_id;
+};
+
+static void wwan_dev_release(struct device *dev)
+{
+	struct wwan_device *wwandev = to_wwan_dev(dev);
+
+	ida_free(&wwan_dev_ids, wwandev->id);
+	kfree(wwandev);
+}
+
+static const struct device_type wwan_dev_type = {
+	.name    = "wwan_dev",
+	.release = wwan_dev_release,
+};
+
+static int wwan_dev_parent_match(struct device *dev, const void *parent)
+{
+	return (dev->type == &wwan_dev_type && dev->parent == parent);
+}
+
+static struct wwan_device *wwan_dev_get_by_parent(struct device *parent)
+{
+	struct device *dev;
+
+	dev = class_find_device(wwan_class, NULL, parent, wwan_dev_parent_match);
+	if (!dev)
+		return ERR_PTR(-ENODEV);
+
+	return to_wwan_dev(dev);
+}
+
+/* This function allocates and registers a new WWAN device OR if a WWAN device
+ * already exist for the given parent, it gets a reference and return it.
+ * This function is not exported (for now), it is called indirectly via
+ * wwan_create_port().
+ */
+static struct wwan_device *wwan_create_dev(struct device *parent)
+{
+	struct wwan_device *wwandev;
+	int err, id;
+
+	/* The 'find-alloc-register' operation must be protected against
+	 * concurrent execution, a WWAN device is possibly shared between
+	 * multiple callers or concurrently unregistered from wwan_remove_dev().
+	 */
+	mutex_lock(&wwan_register_lock);
+
+	/* If wwandev already exist, return it */
+	wwandev = wwan_dev_get_by_parent(parent);
+	if (!IS_ERR(wwandev))
+		goto done_unlock;
+
+	id = ida_alloc(&wwan_dev_ids, GFP_KERNEL);
+	if (id < 0)
+		goto done_unlock;
+
+	wwandev = kzalloc(sizeof(*wwandev), GFP_KERNEL);
+	if (!wwandev) {
+		ida_free(&wwan_dev_ids, id);
+		goto done_unlock;
+	}
+
+	wwandev->dev.parent = parent;
+	wwandev->dev.class = wwan_class;
+	wwandev->dev.type = &wwan_dev_type;
+	wwandev->id = id;
+	dev_set_name(&wwandev->dev, "wwan%d", wwandev->id);
+
+	err = device_register(&wwandev->dev);
+	if (err) {
+		put_device(&wwandev->dev);
+		wwandev = NULL;
+	}
+
+done_unlock:
+	mutex_unlock(&wwan_register_lock);
+
+	return wwandev;
+}
+
+static int is_wwan_child(struct device *dev, void *data)
+{
+	return dev->class == wwan_class;
+}
+
+static void wwan_remove_dev(struct wwan_device *wwandev)
+{
+	int ret;
+
+	/* Prevent concurrent picking from wwan_create_dev */
+	mutex_lock(&wwan_register_lock);
+
+	/* WWAN device is created and registered (get+add) along with its first
+	 * child port, and subsequent port registrations only grab a reference
+	 * (get). The WWAN device must then be unregistered (del+put) along with
+	 * its latest port, and reference simply dropped (put) otherwise.
+	 */
+	ret = device_for_each_child(&wwandev->dev, NULL, is_wwan_child);
+	if (!ret)
+		device_unregister(&wwandev->dev);
+	else
+		put_device(&wwandev->dev);
+
+	mutex_unlock(&wwan_register_lock);
+}
+
+/* ------- WWAN port management ------- */
+
+static void wwan_port_release(struct device *dev)
+{
+	struct wwan_port *port = to_wwan_port(dev);
+
+	ida_free(&minors, MINOR(port->dev.devt));
+	kfree(to_wwan_port(dev));
+}
+
+static const struct device_type wwan_port_dev_type = {
+	.name = "wwan_port",
+	.release = wwan_port_release,
+};
+
+static int wwan_port_minor_match(struct device *dev, const void *minor)
+{
+	return (dev->type == &wwan_port_dev_type &&
+		MINOR(dev->devt) == *(unsigned int *)minor);
+}
+
+static struct wwan_port *wwan_port_get_by_minor(unsigned int minor)
+{
+	struct device *dev;
+
+	dev = class_find_device(wwan_class, NULL, &minor, wwan_port_minor_match);
+	if (!dev)
+		return ERR_PTR(-ENODEV);
+
+	return to_wwan_port(dev);
+}
+
+/* Keep aligned with wwan_port_type enum */
+static const char * const wwan_port_type_str[] = {
+	"AT",
+	"MBIM",
+	"QMI",
+	"QCDM",
+	"FIREHOSE"
+};
+
+struct wwan_port *wwan_create_port(struct device *parent,
+				   enum wwan_port_type type,
+				   const struct file_operations *fops,
+				   void *private_data)
+{
+	struct wwan_device *wwandev;
+	struct wwan_port *port;
+	int minor, err = -ENOMEM;
+
+	if (type >= WWAN_PORT_MAX || !fops)
+		return ERR_PTR(-EINVAL);
+
+	/* A port is always a child of a WWAN device, retrieve (allocate or
+	 * pick) the WWAN device based on the provided parent device.
+	 */
+	wwandev = wwan_create_dev(parent);
+	if (IS_ERR(wwandev))
+		return ERR_PTR(PTR_ERR(wwandev));
+
+	/* A port is exposed as character device, get a minor */
+	minor = ida_alloc_range(&minors, 0, WWAN_MAX_MINORS, GFP_KERNEL);
+	if (minor < 0)
+		goto error_wwandev_remove;
+
+	port = kzalloc(sizeof(*port), GFP_KERNEL);
+	if (!port) {
+		ida_free(&minors, minor);
+		goto error_wwandev_remove;
+	}
+
+	port->type = type;
+	port->fops = fops;
+	port->dev.parent = &wwandev->dev;
+	port->dev.class = wwan_class;
+	port->dev.type = &wwan_port_dev_type;
+	port->dev.devt = MKDEV(wwan_major, minor);
+	dev_set_drvdata(&port->dev, private_data);
+
+	/* create unique name based on wwan device id, port index and type */
+	dev_set_name(&port->dev, "wwan%up%u%s", wwandev->id,
+		     atomic_inc_return(&wwandev->port_id),
+		     wwan_port_type_str[port->type]);
+
+	err = device_register(&port->dev);
+	if (err)
+		goto error_put_device;
+
+	return port;
+
+error_put_device:
+	put_device(&port->dev);
+error_wwandev_remove:
+	wwan_remove_dev(wwandev);
+
+	return ERR_PTR(err);
+}
+EXPORT_SYMBOL_GPL(wwan_create_port);
+
+void wwan_remove_port(struct wwan_port *port)
+{
+	struct wwan_device *wwandev = to_wwan_dev(port->dev.parent);
+
+	dev_set_drvdata(&port->dev, NULL);
+	device_unregister(&port->dev);
+
+	/* Release related wwan device */
+	wwan_remove_dev(wwandev);
+}
+EXPORT_SYMBOL_GPL(wwan_remove_port);
+
+static int wwan_port_open(struct inode *inode, struct file *file)
+{
+	const struct file_operations *new_fops;
+	struct wwan_port *port;
+	int err = 0;
+
+	port = wwan_port_get_by_minor(iminor(inode));
+	if (IS_ERR(port))
+		return PTR_ERR(port);
+
+	/* Place the port private data in the file's private_data so it can
+	 * be used by the file operations, including f_op->open below.
+	 */
+	file->private_data = dev_get_drvdata(&port->dev);
+	stream_open(inode, file);
+
+	/* For now, there is no wwan port ops API, so we simply let the wwan
+	 * port driver implements its own fops.
+	 */
+	new_fops = fops_get(port->fops);
+	replace_fops(file, new_fops);
+	if (file->f_op->open)
+		err = file->f_op->open(inode, file);
+
+	put_device(&port->dev); /* balance wwan_port_get_by_minor */
+
+	return err;
+}
+
+static const struct file_operations wwan_port_fops = {
+	/* these fops will be replaced by registered wwan_port fops */
+	.owner	= THIS_MODULE,
+	.open	= wwan_port_open,
+	.llseek = noop_llseek,
+};
+
+static int __init wwan_init(void)
+{
+	wwan_class = class_create(THIS_MODULE, "wwan");
+	if (IS_ERR(wwan_class))
+		return PTR_ERR(wwan_class);
+
+	/* chrdev used for wwan ports */
+	wwan_major = register_chrdev(0, "wwanport", &wwan_port_fops);
+	if (wwan_major < 0) {
+		class_destroy(wwan_class);
+		return wwan_major;
+	}
+
+	return 0;
+}
+
+static void __exit wwan_exit(void)
+{
+	unregister_chrdev(wwan_major, "wwanport");
+	class_destroy(wwan_class);
+}
+
+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/include/linux/wwan.h b/include/linux/wwan.h
new file mode 100644
index 0000000..e8f2971
--- /dev/null
+++ b/include/linux/wwan.h
@@ -0,0 +1,73 @@ 
+/* 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>
+
+/**
+ * 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
+ * @type: Port type
+ * @fops: Pointer to file operations
+ * @dev: Underlying device
+ */
+struct wwan_port {
+	enum wwan_port_type type;
+	const struct file_operations *fops;
+	struct device dev;
+};
+
+/**
+ * wwan_create_port - Add a new WWAN port
+ * @parent: Device to use as parent and shared by all WWAN ports
+ * @type: WWAN port type
+ * @fops: File operations
+ * @private_data: Pointer to caller private_data
+ *
+ * Allocate and register a new WWAN port. The port will be automatically exposed
+ * to user as a character device. The port will be automatically attached to the
+ * right WWAN device, based on the parent pointer. The parent pointer is the
+ * device shared by all components of a same WWAN modem (e.g. USB dev, PCI dev,
+ * MHI controller...).
+ *
+ * private_data will be placed in the file's private_data so it can be used by
+ * the port file operations.
+ *
+ * This function must be balanced with a call to wwan_destroy_port().
+ *
+ * Returns a valid pointer to wwan_port on success or PTR_ERR on failure
+ */
+struct wwan_port *wwan_create_port(struct device *parent,
+				   enum wwan_port_type type,
+				   const struct file_operations *fops,
+				   void *private_data);
+
+/**
+ * wwan_remove_port - Remove a WWAN port
+ * @port: WWAN port to remove
+ *
+ * Remove a previously created port.
+ */
+void wwan_remove_port(struct wwan_port *port);
+
+#endif /* __WWAN_H */