wwan_hwsim: WWAN device simulator

This driver simulates a set of WWAN device with a set of AT control
ports. It can be used to test WWAN kernel framework as well as user
space tools.
Signed-off-by: Sergey Ryazanov <ryazanov.s.a@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

drivers/net/wwan/Kconfig

@@ -20,6 +20,16 @@ config WWAN_CORE
 	  To compile this driver as a module, choose M here: the module will be
 	  called wwan.
 
+config WWAN_HWSIM
+	tristate "Simulated WWAN device"
+	depends on WWAN_CORE
+	help
+	  This driver is a developer testing tool that can be used to test WWAN
+	  framework.
+
+	  To compile this driver as a module, choose M here: the module will be
+	  called wwan_hwsim.  If unsure, say N.
+
 config MHI_WWAN_CTRL
 	tristate "MHI WWAN control driver for QCOM-based PCIe modems"
 	select WWAN_CORE

drivers/net/wwan/Makefile

@@ -6,4 +6,6 @@
 obj-$(CONFIG_WWAN_CORE) += wwan.o
 wwan-objs += wwan_core.o
 
+obj-$(CONFIG_WWAN_HWSIM) += wwan_hwsim.o
+
 obj-$(CONFIG_MHI_WWAN_CTRL) += mhi_wwan_ctrl.o

drivers/net/wwan/wwan_hwsim.c

+// SPDX-License-Identifier: GPL-2.0-only
+/*
+ * WWAN device simulator for WWAN framework testing.
+ *
+ * Copyright (c) 2021, Sergey Ryazanov <ryazanov.s.a@gmail.com>
+ */
+
+#define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
+
+#include <linux/kernel.h>
+#include <linux/module.h>
+#include <linux/slab.h>
+#include <linux/device.h>
+#include <linux/spinlock.h>
+#include <linux/list.h>
+#include <linux/skbuff.h>
+#include <linux/wwan.h>
+
+static int wwan_hwsim_devsnum = 2;
+module_param_named(devices, wwan_hwsim_devsnum, int, 0444);
+MODULE_PARM_DESC(devices, "Number of simulated devices");
+
+static struct class *wwan_hwsim_class;
+
+static DEFINE_SPINLOCK(wwan_hwsim_devs_lock);
+static LIST_HEAD(wwan_hwsim_devs);
+static unsigned int wwan_hwsim_dev_idx;
+
+struct wwan_hwsim_dev {
+	struct list_head list;
+	unsigned int id;
+	struct device dev;
+	spinlock_t ports_lock;	/* Serialize ports creation/deletion */
+	unsigned int port_idx;
+	struct list_head ports;
+};
+
+struct wwan_hwsim_port {
+	struct list_head list;
+	unsigned int id;
+	struct wwan_hwsim_dev *dev;
+	struct wwan_port *wwan;
+	enum {			/* AT command parser state */
+		AT_PARSER_WAIT_A,
+		AT_PARSER_WAIT_T,
+		AT_PARSER_WAIT_TERM,
+		AT_PARSER_SKIP_LINE,
+	} pstate;
+};
+
+static int wwan_hwsim_port_start(struct wwan_port *wport)
+{
+	struct wwan_hwsim_port *port = wwan_port_get_drvdata(wport);
+
+	port->pstate = AT_PARSER_WAIT_A;
+
+	return 0;
+}
+
+static void wwan_hwsim_port_stop(struct wwan_port *wport)
+{
+}
+
+/* Implements a minimalistic AT commands parser that echo input back and
+ * reply with 'OK' to each input command. See AT command protocol details in the
+ * ITU-T V.250 recomendations document.
+ *
+ * Be aware that this processor is not fully V.250 compliant.
+ */
+static int wwan_hwsim_port_tx(struct wwan_port *wport, struct sk_buff *in)
+{
+	struct wwan_hwsim_port *port = wwan_port_get_drvdata(wport);
+	struct sk_buff *out;
+	int i, n, s;
+
+	/* Estimate a max possible number of commands by counting the number of
+	 * termination chars (S3 param, CR by default). And then allocate the
+	 * output buffer that will be enough to fit the echo and result codes of
+	 * all commands.
+	 */
+	for (i = 0, n = 0; i < in->len; ++i)
+		if (in->data[i] == '\r')
+			n++;
+	n = in->len + n * (2 + 2 + 2);	/* Output buffer size */
+	out = alloc_skb(n, GFP_KERNEL);
+	if (!out)
+		return -ENOMEM;
+
+	for (i = 0, s = 0; i < in->len; ++i) {
+		char c = in->data[i];
+
+		if (port->pstate == AT_PARSER_WAIT_A) {
+			if (c == 'A' || c == 'a')
+				port->pstate = AT_PARSER_WAIT_T;
+			else if (c != '\n')	/* Ignore formating char */
+				port->pstate = AT_PARSER_SKIP_LINE;
+		} else if (port->pstate == AT_PARSER_WAIT_T) {
+			if (c == 'T' || c == 't')
+				port->pstate = AT_PARSER_WAIT_TERM;
+			else
+				port->pstate = AT_PARSER_SKIP_LINE;
+		} else if (port->pstate == AT_PARSER_WAIT_TERM) {
+			if (c != '\r')
+				continue;
+			/* Consume the trailing formatting char as well */
+			if ((i + 1) < in->len && in->data[i + 1] == '\n')
+				i++;
+			n = i - s + 1;
+			memcpy(skb_put(out, n), &in->data[s], n);/* Echo */
+			memcpy(skb_put(out, 6), "\r\nOK\r\n", 6);
+			s = i + 1;
+			port->pstate = AT_PARSER_WAIT_A;
+		} else if (port->pstate == AT_PARSER_SKIP_LINE) {
+			if (c != '\r')
+				continue;
+			port->pstate = AT_PARSER_WAIT_A;
+		}
+	}
+
+	if (i > s) {
+		/* Echo the processed portion of a not yet completed command */
+		n = i - s;
+		memcpy(skb_put(out, n), &in->data[s], n);
+	}
+
+	consume_skb(in);
+
+	wwan_port_rx(wport, out);
+
+	return 0;
+}
+
+static const struct wwan_port_ops wwan_hwsim_port_ops = {
+	.start = wwan_hwsim_port_start,
+	.stop = wwan_hwsim_port_stop,
+	.tx = wwan_hwsim_port_tx,
+};
+
+static struct wwan_hwsim_port *wwan_hwsim_port_new(struct wwan_hwsim_dev *dev)
+{
+	struct wwan_hwsim_port *port;
+	int err;
+
+	port = kzalloc(sizeof(*port), GFP_KERNEL);
+	if (!port)
+		return ERR_PTR(-ENOMEM);
+
+	port->dev = dev;
+
+	spin_lock(&dev->ports_lock);
+	port->id = dev->port_idx++;
+	spin_unlock(&dev->ports_lock);
+
+	port->wwan = wwan_create_port(&dev->dev, WWAN_PORT_AT,
+				      &wwan_hwsim_port_ops,
+				      port);
+	if (IS_ERR(port->wwan)) {
+		err = PTR_ERR(port->wwan);
+		goto err_free_port;
+	}
+
+	return port;
+
+err_free_port:
+	kfree(port);
+
+	return ERR_PTR(err);
+}
+
+static void wwan_hwsim_port_del(struct wwan_hwsim_port *port)
+{
+	wwan_remove_port(port->wwan);
+	kfree(port);
+}
+
+static void wwan_hwsim_dev_release(struct device *sysdev)
+{
+	struct wwan_hwsim_dev *dev = container_of(sysdev, typeof(*dev), dev);
+
+	kfree(dev);
+}
+
+static struct wwan_hwsim_dev *wwan_hwsim_dev_new(void)
+{
+	struct wwan_hwsim_dev *dev;
+	int err;
+
+	dev = kzalloc(sizeof(*dev), GFP_KERNEL);
+	if (!dev)
+		return ERR_PTR(-ENOMEM);
+
+	spin_lock(&wwan_hwsim_devs_lock);
+	dev->id = wwan_hwsim_dev_idx++;
+	spin_unlock(&wwan_hwsim_devs_lock);
+
+	dev->dev.release = wwan_hwsim_dev_release;
+	dev->dev.class = wwan_hwsim_class;
+	dev_set_name(&dev->dev, "hwsim%u", dev->id);
+
+	spin_lock_init(&dev->ports_lock);
+	INIT_LIST_HEAD(&dev->ports);
+
+	err = device_register(&dev->dev);
+	if (err)
+		goto err_free_dev;
+
+	return dev;
+
+err_free_dev:
+	kfree(dev);
+
+	return ERR_PTR(err);
+}
+
+static void wwan_hwsim_dev_del(struct wwan_hwsim_dev *dev)
+{
+	spin_lock(&dev->ports_lock);
+	while (!list_empty(&dev->ports)) {
+		struct wwan_hwsim_port *port;
+
+		port = list_first_entry(&dev->ports, struct wwan_hwsim_port,
+					list);
+		list_del(&port->list);
+		spin_unlock(&dev->ports_lock);
+		wwan_hwsim_port_del(port);
+		spin_lock(&dev->ports_lock);
+	}
+	spin_unlock(&dev->ports_lock);
+
+	device_unregister(&dev->dev);
+	/* Memory will be freed in the device release callback */
+}
+
+static int __init wwan_hwsim_init_devs(void)
+{
+	struct wwan_hwsim_dev *dev;
+	int i, j;
+
+	for (i = 0; i < wwan_hwsim_devsnum; ++i) {
+		dev = wwan_hwsim_dev_new();
+		if (IS_ERR(dev))
+			return PTR_ERR(dev);
+
+		spin_lock(&wwan_hwsim_devs_lock);
+		list_add_tail(&dev->list, &wwan_hwsim_devs);
+		spin_unlock(&wwan_hwsim_devs_lock);
+
+		/* Create a couple of ports per each device to accelerate
+		 * the simulator readiness time.
+		 */
+		for (j = 0; j < 2; ++j) {
+			struct wwan_hwsim_port *port;
+
+			port = wwan_hwsim_port_new(dev);
+			if (IS_ERR(port))
+				return PTR_ERR(port);
+
+			spin_lock(&dev->ports_lock);
+			list_add_tail(&port->list, &dev->ports);
+			spin_unlock(&dev->ports_lock);
+		}
+	}
+
+	return 0;
+}
+
+static void wwan_hwsim_free_devs(void)
+{
+	struct wwan_hwsim_dev *dev;
+
+	spin_lock(&wwan_hwsim_devs_lock);
+	while (!list_empty(&wwan_hwsim_devs)) {
+		dev = list_first_entry(&wwan_hwsim_devs, struct wwan_hwsim_dev,
+				       list);
+		list_del(&dev->list);
+		spin_unlock(&wwan_hwsim_devs_lock);
+		wwan_hwsim_dev_del(dev);
+		spin_lock(&wwan_hwsim_devs_lock);
+	}
+	spin_unlock(&wwan_hwsim_devs_lock);
+}
+
+static int __init wwan_hwsim_init(void)
+{
+	int err;
+
+	if (wwan_hwsim_devsnum < 0 || wwan_hwsim_devsnum > 128)
+		return -EINVAL;
+
+	wwan_hwsim_class = class_create(THIS_MODULE, "wwan_hwsim");
+	if (IS_ERR(wwan_hwsim_class))
+		return PTR_ERR(wwan_hwsim_class);
+
+	err = wwan_hwsim_init_devs();
+	if (err)
+		goto err_clean_devs;
+
+	return 0;
+
+err_clean_devs:
+	wwan_hwsim_free_devs();
+	class_destroy(wwan_hwsim_class);
+
+	return err;
+}
+
+static void __exit wwan_hwsim_exit(void)
+{
+	wwan_hwsim_free_devs();
+	class_destroy(wwan_hwsim_class);
+}
+
+module_init(wwan_hwsim_init);
+module_exit(wwan_hwsim_exit);
+
+MODULE_AUTHOR("Sergey Ryazanov");
+MODULE_DESCRIPTION("Device simulator for WWAN framework");
+MODULE_LICENSE("GPL");