On 20/02/15 17:46, Russell King - ARM Linux wrote:

On Thu, Feb 19, 2015 at 05:08:28PM +0000, Srinivas Kandagatla wrote:

quoted

+static struct class eeprom_class = {
+	.name		= "eeprom",
+	.dev_groups	= eeprom_dev_groups,
+};
+
+int eeprom_register(struct eeprom_device *eeprom)
+{
+	int rval;
+
+	if (!eeprom->regmap || !eeprom->size) {
+		dev_err(eeprom->dev, "Regmap not found\n");
+		return -EINVAL;
+	}
+
+	eeprom->id = ida_simple_get(&eeprom_ida, 0, 0, GFP_KERNEL);
+	if (eeprom->id < 0)
+		return eeprom->id;
+
+	eeprom->edev.class = &eeprom_class;
+	eeprom->edev.parent = eeprom->dev;
+	eeprom->edev.of_node = eeprom->dev ? eeprom->dev->of_node : NULL;
+	dev_set_name(&eeprom->edev, "eeprom%d", eeprom->id);
+
+	device_initialize(&eeprom->edev);
+
+	dev_dbg(&eeprom->edev, "Registering eeprom device %s\n",
+		dev_name(&eeprom->edev));
+
+	rval = device_add(&eeprom->edev);
+	if (rval)
+		return rval;
+
+	mutex_lock(&eeprom_list_mutex);
+	list_add(&eeprom->list, &eeprom_list);
+	mutex_unlock(&eeprom_list_mutex);
+
+	return 0;
+}
+EXPORT_SYMBOL(eeprom_register);
+
+int eeprom_unregister(struct eeprom_device *eeprom)
+{
+	device_del(&eeprom->edev);
+
+	mutex_lock(&eeprom_list_mutex);
+	list_del(&eeprom->list);
+	mutex_unlock(&eeprom_list_mutex);
+
+	return 0;

There's problems with this.  "edev" is embedded into eeprom, and "edev"
is a refcounted structure - it has a lifetime, and the lifetime of
eeprom is thus determined by edev.

What this means is that calling eeprom_unregister() and then freeing
the eeprom structure is a potentially unsafe operation - the memory
backing edev must only be freed when the release method for the
struct device has been called.

Thats a good catch, Yes I see the issue.

Moving the struct eeprom_device allocation to eeprom core.c should 
address this issue. This makes eeprom self contained and can safely free 
the eeprom_device memory in eeprom_class.eeprom_release().

Will fix this in next version.

quoted

+struct eeprom_device {
+	struct regmap		*regmap;
+	int			stride;
+	size_t			size;
+	struct device		*dev;

Failing to understand and address the driver model life time issues is
a major blocker for this patch.  Sorry.