wwan_hwsim: add debugfs management interface

wwan_hwsim creates and removes simulated control ports on module loading
and unloading. It would be helpful to be able to create/remove devices
and ports at run-time to trigger wwan port (un-)register actions without
module reloading.

Some simulator objects (e.g. ports) do not have the underling device and
it is not possible to fully manage the simulator via sysfs. wwan_hsim
intend for developers, so implement it as a self-contained debugfs based
management interface.

Signed-off-by: Sergey Ryazanov <ryazanov.s.a@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

diff --git a/drivers/net/wwan/wwan_hwsim.c b/drivers/net/wwan/wwan_hwsim.c
index 96d25d7..472cae5 100644 (file)
--- a/drivers/net/wwan/wwan_hwsim.c
+++ b/drivers/net/wwan/wwan_hwsim.c
@@ -15,6 +15,8 @@
 #include <linux/list.h>
 #include <linux/skbuff.h>
 #include <linux/wwan.h>
+#include <linux/debugfs.h>
+#include <linux/workqueue.h>
 
 static int wwan_hwsim_devsnum = 2;
 module_param_named(devices, wwan_hwsim_devsnum, int, 0444);
@@ -22,6 +24,9 @@ MODULE_PARM_DESC(devices, "Number of simulated devices");
 
 static struct class *wwan_hwsim_class;
 
+static struct dentry *wwan_hwsim_debugfs_topdir;
+static struct dentry *wwan_hwsim_debugfs_devcreate;
+
 static DEFINE_SPINLOCK(wwan_hwsim_devs_lock);
 static LIST_HEAD(wwan_hwsim_devs);
 static unsigned int wwan_hwsim_dev_idx;
@@ -30,6 +35,9 @@ struct wwan_hwsim_dev {
        struct list_head list;
        unsigned int id;
        struct device dev;
+       struct work_struct del_work;
+       struct dentry *debugfs_topdir;
+       struct dentry *debugfs_portcreate;
        spinlock_t ports_lock;  /* Serialize ports creation/deletion */
        unsigned int port_idx;
        struct list_head ports;
@@ -40,6 +48,8 @@ struct wwan_hwsim_port {
        unsigned int id;
        struct wwan_hwsim_dev *dev;
        struct wwan_port *wwan;
+       struct work_struct del_work;
+       struct dentry *debugfs_topdir;
        enum {                  /* AT command parser state */
                AT_PARSER_WAIT_A,
                AT_PARSER_WAIT_T,
@@ -48,6 +58,12 @@ struct wwan_hwsim_port {
        } pstate;
 };
 
+static const struct file_operations wwan_hwsim_debugfs_portdestroy_fops;
+static const struct file_operations wwan_hwsim_debugfs_portcreate_fops;
+static const struct file_operations wwan_hwsim_debugfs_devdestroy_fops;
+static void wwan_hwsim_port_del_work(struct work_struct *work);
+static void wwan_hwsim_dev_del_work(struct work_struct *work);
+
 static int wwan_hwsim_port_start(struct wwan_port *wport)
 {
        struct wwan_hwsim_port *port = wwan_port_get_drvdata(wport);
@@ -139,6 +155,7 @@ static const struct wwan_port_ops wwan_hwsim_port_ops = {
 static struct wwan_hwsim_port *wwan_hwsim_port_new(struct wwan_hwsim_dev *dev)
 {
        struct wwan_hwsim_port *port;
+       char name[0x10];
        int err;
 
        port = kzalloc(sizeof(*port), GFP_KERNEL);
@@ -159,6 +176,13 @@ static struct wwan_hwsim_port *wwan_hwsim_port_new(struct wwan_hwsim_dev *dev)
                goto err_free_port;
        }
 
+       INIT_WORK(&port->del_work, wwan_hwsim_port_del_work);
+
+       snprintf(name, sizeof(name), "port%u", port->id);
+       port->debugfs_topdir = debugfs_create_dir(name, dev->debugfs_topdir);
+       debugfs_create_file("destroy", 0200, port->debugfs_topdir, port,
+                           &wwan_hwsim_debugfs_portdestroy_fops);
+
        return port;
 
 err_free_port:
@@ -169,10 +193,34 @@ err_free_port:
 
 static void wwan_hwsim_port_del(struct wwan_hwsim_port *port)
 {
+       debugfs_remove(port->debugfs_topdir);
+
+       /* Make sure that there is no pending deletion work */
+       if (current_work() != &port->del_work)
+               cancel_work_sync(&port->del_work);
+
        wwan_remove_port(port->wwan);
        kfree(port);
 }
 
+static void wwan_hwsim_port_del_work(struct work_struct *work)
+{
+       struct wwan_hwsim_port *port =
+                               container_of(work, typeof(*port), del_work);
+       struct wwan_hwsim_dev *dev = port->dev;
+
+       spin_lock(&dev->ports_lock);
+       if (list_empty(&port->list)) {
+               /* Someone else deleting port at the moment */
+               spin_unlock(&dev->ports_lock);
+               return;
+       }
+       list_del_init(&port->list);
+       spin_unlock(&dev->ports_lock);
+
+       wwan_hwsim_port_del(port);
+}
+
 static void wwan_hwsim_dev_release(struct device *sysdev)
 {
        struct wwan_hwsim_dev *dev = container_of(sysdev, typeof(*dev), dev);
@@ -204,6 +252,17 @@ static struct wwan_hwsim_dev *wwan_hwsim_dev_new(void)
        if (err)
                goto err_free_dev;
 
+       INIT_WORK(&dev->del_work, wwan_hwsim_dev_del_work);
+
+       dev->debugfs_topdir = debugfs_create_dir(dev_name(&dev->dev),
+                                                wwan_hwsim_debugfs_topdir);
+       debugfs_create_file("destroy", 0200, dev->debugfs_topdir, dev,
+                           &wwan_hwsim_debugfs_devdestroy_fops);
+       dev->debugfs_portcreate =
+               debugfs_create_file("portcreate", 0200,
+                                   dev->debugfs_topdir, dev,
+                                   &wwan_hwsim_debugfs_portcreate_fops);
+
        return dev;
 
 err_free_dev:
@@ -214,23 +273,136 @@ err_free_dev:
 
 static void wwan_hwsim_dev_del(struct wwan_hwsim_dev *dev)
 {
+       debugfs_remove(dev->debugfs_portcreate);        /* Avoid new ports */
+
        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);
+               list_del_init(&port->list);
                spin_unlock(&dev->ports_lock);
                wwan_hwsim_port_del(port);
                spin_lock(&dev->ports_lock);
        }
        spin_unlock(&dev->ports_lock);
 
+       debugfs_remove(dev->debugfs_topdir);
+
+       /* Make sure that there is no pending deletion work */
+       if (current_work() != &dev->del_work)
+               cancel_work_sync(&dev->del_work);
+
        device_unregister(&dev->dev);
        /* Memory will be freed in the device release callback */
 }
 
+static void wwan_hwsim_dev_del_work(struct work_struct *work)
+{
+       struct wwan_hwsim_dev *dev = container_of(work, typeof(*dev), del_work);
+
+       spin_lock(&wwan_hwsim_devs_lock);
+       if (list_empty(&dev->list)) {
+               /* Someone else deleting device at the moment */
+               spin_unlock(&wwan_hwsim_devs_lock);
+               return;
+       }
+       list_del_init(&dev->list);
+       spin_unlock(&wwan_hwsim_devs_lock);
+
+       wwan_hwsim_dev_del(dev);
+}
+
+static ssize_t wwan_hwsim_debugfs_portdestroy_write(struct file *file,
+                                                   const char __user *usrbuf,
+                                                   size_t count, loff_t *ppos)
+{
+       struct wwan_hwsim_port *port = file->private_data;
+
+       /* We can not delete port here since it will cause a deadlock due to
+        * waiting this callback to finish in the debugfs_remove() call. So,
+        * use workqueue.
+        */
+       schedule_work(&port->del_work);
+
+       return count;
+}
+
+static const struct file_operations wwan_hwsim_debugfs_portdestroy_fops = {
+       .write = wwan_hwsim_debugfs_portdestroy_write,
+       .open = simple_open,
+       .llseek = noop_llseek,
+};
+
+static ssize_t wwan_hwsim_debugfs_portcreate_write(struct file *file,
+                                                  const char __user *usrbuf,
+                                                  size_t count, loff_t *ppos)
+{
+       struct wwan_hwsim_dev *dev = file->private_data;
+       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 count;
+}
+
+static const struct file_operations wwan_hwsim_debugfs_portcreate_fops = {
+       .write = wwan_hwsim_debugfs_portcreate_write,
+       .open = simple_open,
+       .llseek = noop_llseek,
+};
+
+static ssize_t wwan_hwsim_debugfs_devdestroy_write(struct file *file,
+                                                  const char __user *usrbuf,
+                                                  size_t count, loff_t *ppos)
+{
+       struct wwan_hwsim_dev *dev = file->private_data;
+
+       /* We can not delete device here since it will cause a deadlock due to
+        * waiting this callback to finish in the debugfs_remove() call. So,
+        * use workqueue.
+        */
+       schedule_work(&dev->del_work);
+
+       return count;
+}
+
+static const struct file_operations wwan_hwsim_debugfs_devdestroy_fops = {
+       .write = wwan_hwsim_debugfs_devdestroy_write,
+       .open = simple_open,
+       .llseek = noop_llseek,
+};
+
+static ssize_t wwan_hwsim_debugfs_devcreate_write(struct file *file,
+                                                 const char __user *usrbuf,
+                                                 size_t count, loff_t *ppos)
+{
+       struct wwan_hwsim_dev *dev;
+
+       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);
+
+       return count;
+}
+
+static const struct file_operations wwan_hwsim_debugfs_devcreate_fops = {
+       .write = wwan_hwsim_debugfs_devcreate_write,
+       .open = simple_open,
+       .llseek = noop_llseek,
+};
+
 static int __init wwan_hwsim_init_devs(void)
 {
        struct wwan_hwsim_dev *dev;
@@ -272,7 +444,7 @@ static void wwan_hwsim_free_devs(void)
        while (!list_empty(&wwan_hwsim_devs)) {
                dev = list_first_entry(&wwan_hwsim_devs, struct wwan_hwsim_dev,
                                       list);
-               list_del(&dev->list);
+               list_del_init(&dev->list);
                spin_unlock(&wwan_hwsim_devs_lock);
                wwan_hwsim_dev_del(dev);
                spin_lock(&wwan_hwsim_devs_lock);
@@ -291,6 +463,12 @@ static int __init wwan_hwsim_init(void)
        if (IS_ERR(wwan_hwsim_class))
                return PTR_ERR(wwan_hwsim_class);
 
+       wwan_hwsim_debugfs_topdir = debugfs_create_dir("wwan_hwsim", NULL);
+       wwan_hwsim_debugfs_devcreate =
+                       debugfs_create_file("devcreate", 0200,
+                                           wwan_hwsim_debugfs_topdir, NULL,
+                                           &wwan_hwsim_debugfs_devcreate_fops);
+
        err = wwan_hwsim_init_devs();
        if (err)
                goto err_clean_devs;
@@ -299,6 +477,7 @@ static int __init wwan_hwsim_init(void)
 
 err_clean_devs:
        wwan_hwsim_free_devs();
+       debugfs_remove(wwan_hwsim_debugfs_topdir);
        class_destroy(wwan_hwsim_class);
 
        return err;
@@ -306,7 +485,10 @@ err_clean_devs:
 
 static void __exit wwan_hwsim_exit(void)
 {
+       debugfs_remove(wwan_hwsim_debugfs_devcreate);   /* Avoid new devs */
        wwan_hwsim_free_devs();
+       flush_scheduled_work();         /* Wait deletion works completion */
+       debugfs_remove(wwan_hwsim_debugfs_topdir);
        class_destroy(wwan_hwsim_class);
 }