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wwan_hwsim: add debugfs management interface
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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>
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Sergey Ryazanov authored and David S. Miller committed Jun 8, 2021
1 parent f36a111 commit 9ee23f4
Showing 1 changed file with 184 additions and 2 deletions.
186 changes: 184 additions & 2 deletions drivers/net/wwan/wwan_hwsim.c
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Original file line number Diff line number Diff line change
Expand Up @@ -15,13 +15,18 @@
#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);
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;
Expand All @@ -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;
Expand All @@ -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,
Expand All @@ -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);
Expand Down Expand Up @@ -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);
Expand All @@ -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:
Expand All @@ -169,10 +193,34 @@ static struct wwan_hwsim_port *wwan_hwsim_port_new(struct wwan_hwsim_dev *dev)

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);
Expand Down Expand Up @@ -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:
Expand All @@ -214,23 +273,136 @@ static struct wwan_hwsim_dev *wwan_hwsim_dev_new(void)

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;
Expand Down Expand Up @@ -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);
Expand All @@ -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;
Expand All @@ -299,14 +477,18 @@ 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;
}

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);
}

Expand Down

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