hp_accel: do not call ACPI from invalid context

The LED on HP notebooks is connected through ACPI.  That unfortunately
means that it needs to be delayed by using schedule_work() to avoid
calling the ACPI interpreter from an invalid context.

[akpm@linux-foundation.org: use flush_work() rather than sort-of reimplementing it]
Signed-off-by: Pavel Machek <pavel@suse.cz>
Cc: Éric Piel <eric.piel@tremplin-utc.net>
Cc: Len Brown <lenb@kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

drivers/hwmon/hp_accel.c

@@ -3,7 +3,7 @@
  *
  *  Copyright (C) 2007-2008 Yan Burman
  *  Copyright (C) 2008 Eric Piel
- *  Copyright (C) 2008 Pavel Machek
+ *  Copyright (C) 2008-2009 Pavel Machek
  *
  *  This program is free software; you can redistribute it and/or modify
  *  it under the terms of the GNU General Public License as published by
@@ -44,6 +44,36 @@
 #define DRIVER_NAME     "lis3lv02d"
 #define ACPI_MDPS_CLASS "accelerometer"
 
+/* Delayed LEDs infrastructure ------------------------------------ */
+
+/* Special LED class that can defer work */
+struct delayed_led_classdev {
+	struct led_classdev led_classdev;
+	struct work_struct work;
+	enum led_brightness new_brightness;
+
+	unsigned int led;		/* For driver */
+	void (*set_brightness)(struct delayed_led_classdev *data, enum led_brightness value);
+};
+
+static inline void delayed_set_status_worker(struct work_struct *work)
+{
+	struct delayed_led_classdev *data =
+			container_of(work, struct delayed_led_classdev, work);
+
+	data->set_brightness(data, data->new_brightness);
+}
+
+static inline void delayed_sysfs_set(struct led_classdev *led_cdev,
+			      enum led_brightness brightness)
+{
+	struct delayed_led_classdev *data = container_of(led_cdev,
+			     struct delayed_led_classdev, led_classdev);
+	data->new_brightness = brightness;
+	schedule_work(&data->work);
+}
+
+/* HP-specific accelerometer driver ------------------------------------ */
 
 /* For automatic insertion of the module */
 static struct acpi_device_id lis3lv02d_device_ids[] = {
@@ -155,28 +185,27 @@ static struct dmi_system_id lis3lv02d_dmi_ids[] = {
  */
 };
 
-static acpi_status hpled_acpi_write(acpi_handle handle, int reg)
+static void hpled_set(struct delayed_led_classdev *led_cdev, enum led_brightness value)
 {
+	acpi_handle handle = adev.device->handle;
 	unsigned long long ret; /* Not used when writing */
 	union acpi_object in_obj[1];
 	struct acpi_object_list args = { 1, in_obj };
 
 	in_obj[0].type          = ACPI_TYPE_INTEGER;
-	in_obj[0].integer.value = reg;
+	in_obj[0].integer.value = !!value;
 
-	return acpi_evaluate_integer(handle, "ALED", &args, &ret);
-}
-
-static void hpled_set(struct led_classdev *led_cdev,
-			       enum led_brightness value)
-{
-	hpled_acpi_write(adev.device->handle, !!value);
+	acpi_evaluate_integer(handle, "ALED", &args, &ret);
 }
 
-static struct led_classdev hpled_led = {
-	.name			= "hp:red:hddprotection",
-	.default_trigger	= "none",
-	.brightness_set		= hpled_set,
+static struct delayed_led_classdev hpled_led = {
+	.led_classdev = {
+		.name			= "hp::hddprotect",
+		.default_trigger	= "none",
+		.brightness_set		= delayed_sysfs_set,
+		.flags                  = LED_CORE_SUSPENDRESUME,
+	},
+	.set_brightness = hpled_set,
 };
 
 static int lis3lv02d_add(struct acpi_device *device)
@@ -208,13 +237,15 @@ static int lis3lv02d_add(struct acpi_device *device)
 		adev.ac = lis3lv02d_axis_normal;
 	}
 
-	ret = led_classdev_register(NULL, &hpled_led);
+	INIT_WORK(&hpled_led.work, delayed_set_status_worker);
+	ret = led_classdev_register(NULL, &hpled_led.led_classdev);
 	if (ret)
 		return ret;
 
 	ret = lis3lv02d_init_device(&adev);
 	if (ret) {
-		led_classdev_unregister(&hpled_led);
+		flush_work(&hpled_led.work);
+		led_classdev_unregister(&hpled_led.led_classdev);
 		return ret;
 	}
 
@@ -229,7 +260,8 @@ static int lis3lv02d_remove(struct acpi_device *device, int type)
 	lis3lv02d_joystick_disable();
 	lis3lv02d_poweroff(device->handle);
 
-	led_classdev_unregister(&hpled_led);
+	flush_work(&hpled_led.work);
+	led_classdev_unregister(&hpled_led.led_classdev);
 
 	return lis3lv02d_remove_fs();
 }
@@ -240,7 +272,6 @@ static int lis3lv02d_suspend(struct acpi_device *device, pm_message_t state)
 {
 	/* make sure the device is off when we suspend */
 	lis3lv02d_poweroff(device->handle);
-	led_classdev_suspend(&hpled_led);
 	return 0;
 }
 
@@ -253,7 +284,6 @@ static int lis3lv02d_resume(struct acpi_device *device)
 	else
 		lis3lv02d_poweroff(device->handle);
 	mutex_unlock(&adev.lock);
-	led_classdev_resume(&hpled_led);
 	return 0;
 }
 #else