Question

I’m writing a kernel where I need to read certain statistics from iw_statistics structure, here’s the code:

struct net_device *dev; 
struct iw_statistics *wi_stats;
wi_stats = dev->wireless_handlers->get_wireless_stats(dev);

the code compiles correctly, but when trying to run it, the module gets stuck connot get removed … I’m using linux kernel 2.6.35 and my wireless device is up and running, so the structure HAS to have some values in it.

Answer 1

You need to make sure that dev is initialized first. To initialize dev, you can do something like the following:

static struct net_device* getdev()
{
   struct net_device *dev; 
#ifndef CONFIG_WIRELESS_EXT
   return NULL;
#endif     
   dev = first_net_device(&init_net);
   while (dev) {  
         if (dev->wireless_handles != NULL)
                 break;
         dev=next_net_device(dev);
   } 
   return dev; // if not found dev is NULL;
} 

struct iw_statistics *wi_stats=NULL;
struct net_device *dev = getdev();
if (dev) 
    wi_stats = dev->wireless_handlers->get_wireless_stats(dev);
else 
    printk("error finding wireless device");
if (!wi_stats)
    return;  // error wi_stats not configured.