From mboxrd@z Thu Jan  1 00:00:00 1970
From: Johannes Berg <johannes@sipsolutions.net>
Subject: Re: [RFC][PATCH] Fix another namespace issue with devices assigned
 to  classes
Date: Mon, 07 Jun 2010 12:14:46 +0200
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Cc: "Eric W. Biederman" <ebiederm@xmission.com>,
	Greg KH <greg@kroah.com>, netdev <netdev@vger.kernel.org>
To: Kay Sievers <kay.sievers@vrfy.org>
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On Mon, 2010-06-07 at 11:53 +0200, Kay Sievers wrote:

> > Can you please tell me then how to device_create() without a class? I
> > cannot seem to create devices without a class at all, even using manual
> > allocation (yuck) and device_register crashes the kernel.
> 
> Right, this "convenience API" does not exist for buses. It's not doing
> much, just allocates a "struct device" and fills in the few values and
> calls device_register().
> 
> Does your device create a device node? If not, device_create() should
> not be used anyway, because the corresponding device_destroy() will
> not do anything.

No, it doesn't need a dev node. I tried this:

+               data->dev = kzalloc(sizeof(struct device), GFP_KERNEL);
+               if (!data->dev) {
                        err = -ENOMEM;
                        goto failed_drvdata;
                }
+
+               dev_set_name(data->dev, "hwsim%d", i);
+               data->dev->bus = &hwsim_bus;
                data->dev->driver = &mac80211_hwsim_driver;
 
+               err = device_register(data->dev);
+               if (err) {
+                       printk(KERN_DEBUG
+                              "mac80211_hwsim: device_register failed (%d)\n",
+                              err);
+                       goto failed_drvdata;
+               }

(ignore the pluses, snipped from a patch) but it ran into a null ptr
deref?

johannes