Re: [RFC PATCH 5/6] ACPI: Introduce ACPI I2C controller enumeration driver

+acpi_status __init i2c_enumerate_slave(acpi_handle handle, u32 level,
+				       void *data, void **return_value)
+{
+	int result;
+	acpi_status status;
+	struct acpi_buffer buffer;
+	struct acpi_resource *resource;
+	struct acpi_resource_gpio *gpio;
+	struct acpi_resource_i2c_serialbus *i2c;
+	int i;
+	struct acpi_i2c_root *root = data;
+	struct i2c_board_info info;
+	struct acpi_device *device;
+
+	if (acpi_bus_get_device(handle, &device))
+		return AE_OK;
+
+	status = acpi_get_current_resources(handle, &buffer);
+	if (ACPI_FAILURE(status)) {
+		dev_err(&device->dev, "Failed to get ACPI resources\n");
+		return AE_OK;
+	}
+
+	for (i = 0; i < buffer.length; i += sizeof(struct acpi_resource)) {
+		resource = (struct acpi_resource *)(buffer.pointer + i);
+
+		switch (resource->type) {
+		case ACPI_RESOURCE_TYPE_GPIO:
+			gpio = &resource->data.gpio;
+
+			if (gpio->connection_type == ACPI_RESOURCE_GPIO_TYPE_INT) {
+				result =
+				    acpi_device_get_gpio_irq
+				    (gpio->resource_source.string_ptr,
+				     gpio->pin_table[0], &info.irq);

+				if (result)
+					dev_err(&device->dev,
+						"Failed to get IRQ\n");
+			}
+			break;
+		case ACPI_RESOURCE_TYPE_SERIAL_BUS:
+			i2c = &resource->data.i2c_serial_bus;
+
+			info.addr = i2c->slave_address;
+			break;
+		default:
+			break;
+		}
+	}
+
+	add_slave(root, &info);
+
+	kfree(buffer.pointer);
+	return AE_OK;
+}
+
+static int __devinit acpi_i2c_root_add(struct acpi_device *device)
+{
+	acpi_status status;
+	struct acpi_i2c_root *root;
+	struct resource *resources;
+	int result;
+
+	if (!device->pnp.unique_id) {
+		dev_err(&device->dev,
+			"Unsupported ACPI I2C controller. No UID\n");

+		return -ENODEV;
+	}
+
+	root = kzalloc(sizeof(struct acpi_i2c_root), GFP_KERNEL);
+	if (!root)
+		return -ENOMEM;
+
+	root->device = device;
+
+	kstrtoint(device->pnp.unique_id, 10, &root->busnum);
+
+	/* enumerate I2C controller */
+	root->pdev =
+	    platform_device_alloc(acpi_device_hid(device), root->busnum);
+	if (!root->pdev) {
+		dev_err(&device->dev, "Failed to alloc platform device\n");
+		goto err;
+	}
+
+	result = acpi_get_generic_resources(device, &resources);
+	if (result < 0) {
+		dev_err(&device->dev, "Failed to get resources\n");
+		goto err;
+	}
+
+	platform_device_add_resources(root->pdev, resources, result);
+	platform_device_add(root->pdev);
+
+	/* enumerate I2C slave devices */
+	status = acpi_walk_namespace(ACPI_TYPE_DEVICE, root->device->handle, 1,
+				     i2c_enumerate_slave, NULL, root, NULL);
+
+	if (ACPI_FAILURE(status)) {
+		dev_err(&root->device->dev, "i2c ACPI namespace walk error!\n");
+		kfree(root);
+		return -ENODEV;
+	}
+
+	register_slaves(root);
+
+	return 0;
+err:
+	kfree(root);
+	return -ENODEV;
+}