i2c: Convert the pcf8575 driver to a new-style i2c driver

The new-style pcf8575 driver implements the optional detect() callback
to cover the use cases of the legacy driver.

Warning: users will now have to use the force module parameter to get
the driver to attach to their device. That's not a bad thing as these
devices can't be detected anyway.

Note that this doesn't change the fact that this driver is deprecated
in favor of gpio/pcf857x.

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

Documentation/i2c/chips/pcf8575

···
 ---------
 
 There is no method known to detect whether a chip on a given I2C address is
-a PCF8575 or whether it is any other I2C device. So there are two alternatives
-to let the driver find the installed PCF8575 devices:
-- Load this driver after any other I2C driver for I2C devices with addresses
-  in the range 0x20 .. 0x27.
-- Pass the I2C bus and address of the installed PCF8575 devices explicitly to
-  the driver at load time via the probe=... or force=... parameters.
+a PCF8575 or whether it is any other I2C device, so you have to pass the I2C
+bus and address of the installed PCF8575 devices explicitly to the driver at
+load time via the force=... parameter.
 
 /sys interface
 --------------

drivers/i2c/chips/pcf8575.c

···
 #include <linux/slab.h>  /* kzalloc() */
 #include <linux/sysfs.h> /* sysfs_create_group() */
 
-/* Addresses to scan */
-static const unsigned short normal_i2c[] = {
-	0x20, 0x21, 0x22, 0x23, 0x24, 0x25, 0x26, 0x27,
-	I2C_CLIENT_END
-};
+/* Addresses to scan: none, device can't be detected */
+static const unsigned short normal_i2c[] = { I2C_CLIENT_END };
 
 /* Insmod parameters */
 I2C_CLIENT_INSMOD;
···
 
 /* Each client has this additional data */
 struct pcf8575_data {
-	struct i2c_client client;
 	int write;		/* last written value, or error code */
-};
-
-static int pcf8575_attach_adapter(struct i2c_adapter *adapter);
-static int pcf8575_detect(struct i2c_adapter *adapter, int address, int kind);
-static int pcf8575_detach_client(struct i2c_client *client);
-
-/* This is the driver that will be inserted */
-static struct i2c_driver pcf8575_driver = {
-	.driver = {
-		.owner	= THIS_MODULE,
-		.name	= "pcf8575",
-	},
-	.attach_adapter	= pcf8575_attach_adapter,
-	.detach_client	= pcf8575_detach_client,
 };
 
 /* following are the sysfs callback functions */
···
  * Real code
  */
 
-static int pcf8575_attach_adapter(struct i2c_adapter *adapter)
+/* Return 0 if detection is successful, -ENODEV otherwise */
+static int pcf8575_detect(struct i2c_client *client, int kind,
+			  struct i2c_board_info *info)
 {
-	return i2c_probe(adapter, &addr_data, pcf8575_detect);
-}
-
-/* This function is called by i2c_probe */
-static int pcf8575_detect(struct i2c_adapter *adapter, int address, int kind)
-{
-	struct i2c_client *client;
-	struct pcf8575_data *data;
-	int err = 0;
+	struct i2c_adapter *adapter = client->adapter;
 
 	if (!i2c_check_functionality(adapter, I2C_FUNC_I2C))
-		goto exit;
+		return -ENODEV;
 
-	/* OK. For now, we presume we have a valid client. We now create the
-	   client structure, even though we cannot fill it completely yet. */
+	/* This is the place to detect whether the chip at the specified
+	   address really is a PCF8575 chip. However, there is no method known
+	   to detect whether an I2C chip is a PCF8575 or any other I2C chip. */
+
+	strlcpy(info->type, "pcf8575", I2C_NAME_SIZE);
+
+	return 0;
+}
+
+static int pcf8575_probe(struct i2c_client *client,
+			 const struct i2c_device_id *id)
+{
+	struct pcf8575_data *data;
+	int err;
+
 	data = kzalloc(sizeof(struct pcf8575_data), GFP_KERNEL);
 	if (!data) {
 		err = -ENOMEM;
 		goto exit;
 	}
 
-	client = &data->client;
 	i2c_set_clientdata(client, data);
-	client->addr = address;
-	client->adapter = adapter;
-	client->driver = &pcf8575_driver;
-	strlcpy(client->name, "pcf8575", I2C_NAME_SIZE);
 	data->write = -EAGAIN;
-
-	/* This is the place to detect whether the chip at the specified
-	   address really is a PCF8575 chip. However, there is no method known
-	   to detect whether an I2C chip is a PCF8575 or any other I2C chip. */
-
-	/* Tell the I2C layer a new client has arrived */
-	err = i2c_attach_client(client);
-	if (err)
-		goto exit_free;
 
 	/* Register sysfs hooks */
 	err = sysfs_create_group(&client->dev.kobj, &pcf8575_attr_group);
 	if (err)
-		goto exit_detach;
+		goto exit_free;
 
 	return 0;
 
-exit_detach:
-	i2c_detach_client(client);
 exit_free:
 	kfree(data);
 exit:
 	return err;
 }
 
-static int pcf8575_detach_client(struct i2c_client *client)
+static int pcf8575_remove(struct i2c_client *client)
 {
-	int err;
-
 	sysfs_remove_group(&client->dev.kobj, &pcf8575_attr_group);
-
-	err = i2c_detach_client(client);
-	if (err)
-		return err;
-
 	kfree(i2c_get_clientdata(client));
 	return 0;
 }
+
+static const struct i2c_device_id pcf8575_id[] = {
+	{ "pcf8575", 0 },
+	{ }
+};
+
+static struct i2c_driver pcf8575_driver = {
+	.driver = {
+		.owner	= THIS_MODULE,
+		.name	= "pcf8575",
+	},
+	.probe		= pcf8575_probe,
+	.remove		= pcf8575_remove,
+	.id_table	= pcf8575_id,
+
+	.detect		= pcf8575_detect,
+	.address_data	= &addr_data,
+};
 
 static int __init pcf8575_init(void)
 {