platform/x86: wmi: Turn WMI into a bus driver

WMI is logically a bus: the WMI driver binds to an ACPI node (or
more than one), and each instance of the WMI driver enumerates its
children and hopes that drivers will attach to the children that are
useful.

This patch gives WMI a driver model bus type and the ability to
match to drivers. The bus itself is a device in the new "wmi_bus"
class, and all of the individual WMI devices are slotted into the
device hierarchy correctly.
Signed-off-by: Andy Lutomirski <luto@kernel.org>
Cc: Andy Lutomirski <luto@amacapital.net>
Cc: Mario Limonciello <mario_limonciello@dell.com>
Cc: Pali Rohár <pali.rohar@gmail.com>
Cc: linux-kernel@vger.kernel.org
Cc: platform-driver-x86@vger.kernel.org
Cc: linux-acpi@vger.kernel.org
Acked-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
Signed-off-by: Darren Hart (VMware) <dvhart@infradead.org>

drivers/platform/x86/wmi.c

@@ -37,6 +37,7 @@
 #include <linux/acpi.h>
 #include <linux/slab.h>
 #include <linux/module.h>
+#include <linux/wmi.h>
 #include <linux/uuid.h>
 
 ACPI_MODULE_NAME("wmi");
@@ -44,8 +45,6 @@ MODULE_AUTHOR("Carlos Corbacho");
 MODULE_DESCRIPTION("ACPI-WMI Mapping Driver");
 MODULE_LICENSE("GPL");
 
-#define ACPI_WMI_CLASS "wmi"
-
 static LIST_HEAD(wmi_block_list);
 
 struct guid_block {
@@ -62,12 +61,12 @@ struct guid_block {
 };
 
 struct wmi_block {
+	struct wmi_device dev;
 	struct list_head list;
 	struct guid_block gblock;
 	struct acpi_device *acpi_device;
 	wmi_notify_handler handler;
 	void *handler_data;
-	struct device dev;
 };
 
 
@@ -102,8 +101,8 @@ static const struct acpi_device_id wmi_device_ids[] = {
 MODULE_DEVICE_TABLE(acpi, wmi_device_ids);
 
 static struct acpi_driver acpi_wmi_driver = {
-	.name = "wmi",
-	.class = ACPI_WMI_CLASS,
+	.name = "acpi-wmi",
+	.owner = THIS_MODULE,
 	.ids = wmi_device_ids,
 	.ops = {
 		.add = acpi_wmi_add,
@@ -545,77 +544,146 @@ bool wmi_has_guid(const char *guid_string)
 }
 EXPORT_SYMBOL_GPL(wmi_has_guid);
 
+static struct wmi_block *dev_to_wblock(struct device *dev)
+{
+	return container_of(dev, struct wmi_block, dev.dev);
+}
+
+static struct wmi_device *dev_to_wdev(struct device *dev)
+{
+	return container_of(dev, struct wmi_device, dev);
+}
+
 /*
  * sysfs interface
  */
 static ssize_t modalias_show(struct device *dev, struct device_attribute *attr,
 			     char *buf)
 {
-	struct wmi_block *wblock;
-
-	wblock = dev_get_drvdata(dev);
-	if (!wblock) {
-		strcat(buf, "\n");
-		return strlen(buf);
-	}
+	struct wmi_block *wblock = dev_to_wblock(dev);
 
 	return sprintf(buf, "wmi:%pUL\n", wblock->gblock.guid);
 }
 static DEVICE_ATTR_RO(modalias);
 
+static ssize_t guid_show(struct device *dev, struct device_attribute *attr,
+			 char *buf)
+{
+	struct wmi_block *wblock = dev_to_wblock(dev);
+
+	return sprintf(buf, "%pUL\n", wblock->gblock.guid);
+}
+static DEVICE_ATTR_RO(guid);
+
 static struct attribute *wmi_attrs[] = {
 	&dev_attr_modalias.attr,
+	&dev_attr_guid.attr,
 	NULL,
 };
 ATTRIBUTE_GROUPS(wmi);
 
 static int wmi_dev_uevent(struct device *dev, struct kobj_uevent_env *env)
 {
-	char guid_string[37];
+	struct wmi_block *wblock = dev_to_wblock(dev);
 
-	struct wmi_block *wblock;
-
-	if (add_uevent_var(env, "MODALIAS="))
+	if (add_uevent_var(env, "MODALIAS=wmi:%pUL", wblock->gblock.guid))
 		return -ENOMEM;
 
-	wblock = dev_get_drvdata(dev);
-	if (!wblock)
+	if (add_uevent_var(env, "WMI_GUID=%pUL", wblock->gblock.guid))
 		return -ENOMEM;
 
-	sprintf(guid_string, "%pUL", wblock->gblock.guid);
+	return 0;
+}
+
+static void wmi_dev_release(struct device *dev)
+{
+	struct wmi_block *wblock = dev_to_wblock(dev);
 
-	strcpy(&env->buf[env->buflen - 1], "wmi:");
-	memcpy(&env->buf[env->buflen - 1 + 4], guid_string, 36);
-	env->buflen += 40;
+	kfree(wblock);
+}
+
+static int wmi_dev_match(struct device *dev, struct device_driver *driver)
+{
+	struct wmi_driver *wmi_driver =
+		container_of(driver, struct wmi_driver, driver);
+	struct wmi_block *wblock = dev_to_wblock(dev);
+	const struct wmi_device_id *id = wmi_driver->id_table;
+
+	while (id->guid_string) {
+		uuid_le driver_guid;
+
+		if (WARN_ON(uuid_le_to_bin(id->guid_string, &driver_guid)))
+			continue;
+		if (!memcmp(&driver_guid, wblock->gblock.guid, 16))
+			return 1;
+
+		id++;
+	}
 
 	return 0;
 }
 
-static void wmi_dev_free(struct device *dev)
+static int wmi_dev_probe(struct device *dev)
 {
-	struct wmi_block *wmi_block = container_of(dev, struct wmi_block, dev);
+	struct wmi_block *wblock = dev_to_wblock(dev);
+	struct wmi_driver *wdriver =
+		container_of(dev->driver, struct wmi_driver, driver);
+	int ret = 0;
 
-	kfree(wmi_block);
+	if (ACPI_FAILURE(wmi_method_enable(wblock, 1)))
+		dev_warn(dev, "failed to enable device -- probing anyway\n");
+
+	if (wdriver->probe) {
+		ret = wdriver->probe(dev_to_wdev(dev));
+		if (ret != 0 && ACPI_FAILURE(wmi_method_enable(wblock, 0)))
+			dev_warn(dev, "failed to disable device\n");
+	}
+
+	return ret;
 }
 
-static struct class wmi_class = {
+static int wmi_dev_remove(struct device *dev)
+{
+	struct wmi_block *wblock = dev_to_wblock(dev);
+	struct wmi_driver *wdriver =
+		container_of(dev->driver, struct wmi_driver, driver);
+	int ret = 0;
+
+	if (wdriver->remove)
+		ret = wdriver->remove(dev_to_wdev(dev));
+
+	if (ACPI_FAILURE(wmi_method_enable(wblock, 0)))
+		dev_warn(dev, "failed to disable device\n");
+
+	return ret;
+}
+
+static struct class wmi_bus_class = {
+	.name = "wmi_bus",
+};
+
+static struct bus_type wmi_bus_type = {
 	.name = "wmi",
-	.dev_release = wmi_dev_free,
-	.dev_uevent = wmi_dev_uevent,
 	.dev_groups = wmi_groups,
+	.match = wmi_dev_match,
+	.uevent = wmi_dev_uevent,
+	.probe = wmi_dev_probe,
+	.remove = wmi_dev_remove,
 };
 
-static int wmi_create_device(const struct guid_block *gblock,
+static int wmi_create_device(struct device *wmi_bus_dev,
+			     const struct guid_block *gblock,
 			     struct wmi_block *wblock,
 			     struct acpi_device *device)
 {
-	wblock->dev.class = &wmi_class;
+	wblock->dev.dev.bus = &wmi_bus_type;
+	wblock->dev.dev.parent = wmi_bus_dev;
 
-	dev_set_name(&wblock->dev, "%pUL", gblock->guid);
+	dev_set_name(&wblock->dev.dev, "%pUL", gblock->guid);
 
-	dev_set_drvdata(&wblock->dev, wblock);
+	wblock->dev.dev.release = wmi_dev_release;
 
-	return device_register(&wblock->dev);
+	return device_register(&wblock->dev.dev);
 }
 
 static void wmi_free_devices(struct acpi_device *device)
@@ -626,8 +694,8 @@ static void wmi_free_devices(struct acpi_device *device)
 	list_for_each_entry_safe(wblock, next, &wmi_block_list, list) {
 		if (wblock->acpi_device == device) {
 			list_del(&wblock->list);
-			if (wblock->dev.class)
-				device_unregister(&wblock->dev);
+			if (wblock->dev.dev.bus)
+				device_unregister(&wblock->dev.dev);
 			else
 				kfree(wblock);
 		}
@@ -659,7 +727,7 @@ static bool guid_already_parsed(struct acpi_device *device,
 /*
  * Parse the _WDG method for the GUID data blocks
  */
-static int parse_wdg(struct acpi_device *device)
+static int parse_wdg(struct device *wmi_bus_dev, struct acpi_device *device)
 {
 	struct acpi_buffer out = {ACPI_ALLOCATE_BUFFER, NULL};
 	union acpi_object *obj;
@@ -703,7 +771,8 @@ static int parse_wdg(struct acpi_device *device)
 		  for device creation.
 		*/
 		if (!guid_already_parsed(device, gblock[i].guid)) {
-			retval = wmi_create_device(&gblock[i], wblock, device);
+			retval = wmi_create_device(wmi_bus_dev, &gblock[i],
+						   wblock, device);
 			if (retval) {
 				wmi_free_devices(device);
 				goto out_free_pointer;
@@ -803,12 +872,15 @@ static int acpi_wmi_remove(struct acpi_device *device)
 	acpi_remove_address_space_handler(device->handle,
 				ACPI_ADR_SPACE_EC, &acpi_wmi_ec_space_handler);
 	wmi_free_devices(device);
+	device_unregister((struct device *)acpi_driver_data(device));
+	device->driver_data = NULL;
 
 	return 0;
 }
 
 static int acpi_wmi_add(struct acpi_device *device)
 {
+	struct device *wmi_bus_dev;
 	acpi_status status;
 	int error;
 
@@ -821,14 +893,25 @@ static int acpi_wmi_add(struct acpi_device *device)
 		return -ENODEV;
 	}
 
-	error = parse_wdg(device);
+	wmi_bus_dev = device_create(&wmi_bus_class, &device->dev, MKDEV(0, 0),
+				    NULL, "wmi_bus-%s", dev_name(&device->dev));
+	if (IS_ERR(wmi_bus_dev)) {
+		error = PTR_ERR(wmi_bus_dev);
+		goto err_remove_handler;
+	}
+	device->driver_data = wmi_bus_dev;
+
+	error = parse_wdg(wmi_bus_dev, device);
 	if (error) {
 		pr_err("Failed to parse WDG method\n");
-		goto err_remove_handler;
+		goto err_remove_busdev;
 	}
 
 	return 0;
 
+err_remove_busdev:
+	device_unregister(wmi_bus_dev);
+
 err_remove_handler:
 	acpi_remove_address_space_handler(device->handle,
 					  ACPI_ADR_SPACE_EC,
@@ -837,6 +920,22 @@ static int acpi_wmi_add(struct acpi_device *device)
 	return error;
 }
 
+int __must_check __wmi_driver_register(struct wmi_driver *driver,
+				       struct module *owner)
+{
+	driver->driver.owner = owner;
+	driver->driver.bus = &wmi_bus_type;
+
+	return driver_register(&driver->driver);
+}
+EXPORT_SYMBOL(__wmi_driver_register);
+
+void wmi_driver_unregister(struct wmi_driver *driver)
+{
+	driver_unregister(&driver->driver);
+}
+EXPORT_SYMBOL(wmi_driver_unregister);
+
 static int __init acpi_wmi_init(void)
 {
 	int error;
@@ -844,24 +943,36 @@ static int __init acpi_wmi_init(void)
 	if (acpi_disabled)
 		return -ENODEV;
 
-	error = class_register(&wmi_class);
+	error = class_register(&wmi_bus_class);
 	if (error)
 		return error;
 
+	error = bus_register(&wmi_bus_type);
+	if (error)
+		goto err_unreg_class;
+
 	error = acpi_bus_register_driver(&acpi_wmi_driver);
 	if (error) {
 		pr_err("Error loading mapper\n");
-		class_unregister(&wmi_class);
-		return error;
+		goto err_unreg_bus;
 	}
 
 	return 0;
+
+err_unreg_class:
+	class_unregister(&wmi_bus_class);
+
+err_unreg_bus:
+	bus_unregister(&wmi_bus_type);
+
+	return error;
 }
 
 static void __exit acpi_wmi_exit(void)
 {
 	acpi_bus_unregister_driver(&acpi_wmi_driver);
-	class_unregister(&wmi_class);
+	class_unregister(&wmi_bus_class);
+	bus_unregister(&wmi_bus_type);
 }
 
 subsys_initcall(acpi_wmi_init);

include/linux/wmi.h

+/*
+ * wmi.h - ACPI WMI interface
+ *
+ * Copyright (c) 2015 Andrew Lutomirski
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License version 2 as
+ * published by the Free Software Foundation.
+ *
+ * This program is distributed in the hope that it will be useful, but
+ * WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+ * General Public License for more details.
+ */
+
+#ifndef _LINUX_WMI_H
+#define _LINUX_WMI_H
+
+#include <linux/device.h>
+#include <linux/acpi.h>
+
+struct wmi_device {
+	struct device dev;
+};
+
+struct wmi_device_id {
+	const char *guid_string;
+};
+
+struct wmi_driver {
+	struct device_driver driver;
+	const struct wmi_device_id *id_table;
+
+	int (*probe)(struct wmi_device *wdev);
+	int (*remove)(struct wmi_device *wdev);
+};
+
+extern int __must_check __wmi_driver_register(struct wmi_driver *driver,
+					      struct module *owner);
+extern void wmi_driver_unregister(struct wmi_driver *driver);
+#define wmi_driver_register(driver) __wmi_driver_register((driver), THIS_MODULE)
+
+#define module_wmi_driver(__wmi_driver) \
+	module_driver(__wmi_driver, wmi_driver_register, \
+		      wmi_driver_unregister)
+
+#endif