Driver core: change add_uevent_var to use a struct

This changes the uevent buffer functions to use a struct instead of a
long list of parameters. It does no longer require the caller to do the
proper buffer termination and size accounting, which is currently wrong
in some places. It fixes a known bug where parts of the uevent
environment are overwritten because of wrong index calculations.

Many thanks to Mathieu Desnoyers for finding bugs and improving the
error handling.

Signed-off-by: Kay Sievers <kay.sievers@vrfy.org>
Cc: Mathieu Desnoyers <mathieu.desnoyers@polymtl.ca>
Cc: Cornelia Huck <cornelia.huck@de.ibm.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>

drivers/i2c/i2c-core.c

@@ -67,20 +67,16 @@ static int i2c_device_match(struct device *dev, struct device_driver *drv)
 #ifdef	CONFIG_HOTPLUG
 
 /* uevent helps with hotplug: modprobe -q $(MODALIAS) */
-static int i2c_device_uevent(struct device *dev, char **envp, int num_envp,
-		      char *buffer, int buffer_size)
+static int i2c_device_uevent(struct device *dev, struct kobj_uevent_env *env)
 {
 	struct i2c_client	*client = to_i2c_client(dev);
-	int			i = 0, length = 0;
 
 	/* by definition, legacy drivers can't hotplug */
 	if (dev->driver || !client->driver_name)
 		return 0;
 
-	if (add_uevent_var(envp, num_envp, &i, buffer, buffer_size, &length,
-			"MODALIAS=%s", client->driver_name))
+	if (add_uevent_var(env, "MODALIAS=%s", client->driver_name))
 		return -ENOMEM;
-	envp[i] = NULL;
 	dev_dbg(dev, "uevent\n");
 	return 0;
 }