i2c: Migration aids for i2c_adapter.dev removal

Flag i2c_adapter.dev for removal after userspace tools get upgraded, and
include a near-term code migration aid to facilitate this:

- The class device gets the name attribute it should have had. This
was previously (wrongly) associated with the i2c_adapter.dev node.
Sysfs based tools and libraries can start converting right away.

- Issue a warning for legacy adapter drivers that don't provide any
physical device node; so systems with those drivers will know to
fix this problem earlier.

This is one of a series of patches to help the I2C stack become a better
citizen of the Linux Driver Model world.

Signed-off-by: David Brownell <[e-mail]>
Signed-off-by: Jean Delvare <[e-mail]>

Documentation/feature-removal-schedule.txt

···
 
 ---------------------------
 
+What:	i2c_adapter.dev
+	i2c_adapter.list
+When:	July 2007
+Why:	Superfluous, given i2c_adapter.class_dev:
+	  * The "dev" was a stand-in for the physical device node that legacy
+	    drivers would not have; but now it's almost always present.  Any
+	    remaining legacy drivers must upgrade (they now trigger warnings).
+	  * The "list" duplicates class device children.
+	The delay in removing this is so upgraded lm_sensors and libsensors
+	can get deployed.  (Removal causes minor changes in the sysfs layout,
+	notably the location of the adapter type name and parenting the i2c
+	client hardware directly from their controller.)
+Who:	Jean Delvare <[e-mail]>,
+	David Brownell <[e-mail]>
+
+---------------------------
+
 What:	IPv4 only connection tracking/NAT/helpers
 When:	2.6.22
 Why:	The new layer 3 independant connection tracking replaces the old

drivers/i2c/i2c-core.c

···
 	.bus = &i2c_bus_type,
 };
 
+/* ------------------------------------------------------------------------- */
+
+/* I2C bus adapters -- one roots each I2C or SMBUS segment */
+
 static void i2c_adapter_class_dev_release(struct class_device *dev)
 {
 	struct i2c_adapter *adap = class_dev_to_i2c_adapter(dev);
 	complete(&adap->class_dev_released);
 }
 
+static ssize_t i2c_adapter_show_name(struct class_device *cdev, char *buf)
+{
+	struct i2c_adapter *adap = class_dev_to_i2c_adapter(cdev);
+	return sprintf(buf, "%s\n", adap->name);
+}
+
+static struct class_device_attribute i2c_adapter_attrs[] = {
+	__ATTR(name, S_IRUGO, i2c_adapter_show_name, NULL),
+	{ },
+};
+
 struct class i2c_adapter_class = {
-	.owner =	THIS_MODULE,
-	.name =		"i2c-adapter",
-	.release =	&i2c_adapter_class_dev_release,
+	.owner			= THIS_MODULE,
+	.name			= "i2c-adapter",
+	.class_dev_attrs	= i2c_adapter_attrs,
+	.release		= &i2c_adapter_class_dev_release,
 };
 
 static ssize_t show_adapter_name(struct device *dev, struct device_attribute *attr, char *buf)
···
 	 * If the parent pointer is not set up,
 	 * we add this adapter to the host bus.
 	 */
-	if (adap->dev.parent == NULL)
+	if (adap->dev.parent == NULL) {
 		adap->dev.parent = &platform_bus;
+		printk(KERN_WARNING "**WARNING** I2C adapter driver [%s] "
+		       "forgot to specify physical device; fix it!\n",
+		       adap->name);
+	}
 	sprintf(adap->dev.bus_id, "i2c-%d", adap->nr);
 	adap->dev.driver = &i2c_adapter_driver;
 	adap->dev.release = &i2c_adapter_dev_release;