[RFC 1/2] ACPI: platform_profile: Add support for notification chains

[Mario Limonciello <mario.limonciello@xxxxxxx>]

Allow other drivers to initialize relative to current active
profile and react to platform profile changes.

Drivers wishing to utilize this should register for notification
at module load and unregister when unloading.

Notifications will come in the from a notifier call.

Signed-off-by: Mario Limonciello <mario.limonciello@xxxxxxx>
---
 drivers/acpi/platform_profile.c  | 52 +++++++++++++++++++++++++++-----
 include/linux/platform_profile.h | 10 ++++++
 2 files changed, 55 insertions(+), 7 deletions(-)

diff --git a/drivers/acpi/platform_profile.c b/drivers/acpi/platform_profile.c
index d418462ab791..ca5d962020a2 100644
--- a/drivers/acpi/platform_profile.c
+++ b/drivers/acpi/platform_profile.c
@@ -21,6 +21,24 @@ static const char * const profile_names[] = {
 	[PLATFORM_PROFILE_PERFORMANCE] = "performance",
 };
 static_assert(ARRAY_SIZE(profile_names) == PLATFORM_PROFILE_LAST);
+static BLOCKING_NOTIFIER_HEAD(platform_profile_chain_head);
+
+int platform_profile_register_notifier(struct notifier_block *nb)
+{
+	return blocking_notifier_chain_register(&platform_profile_chain_head, nb);
+}
+EXPORT_SYMBOL_GPL(platform_profile_register_notifier);
+
+int platform_profile_unregister_notifier(struct notifier_block *nb)
+{
+	return blocking_notifier_chain_unregister(&platform_profile_chain_head, nb);
+}
+EXPORT_SYMBOL_GPL(platform_profile_unregister_notifier);
+
+static void platform_profile_call_notifier(unsigned long action, void *data)
+{
+	blocking_notifier_call_chain(&platform_profile_chain_head, action, data);
+}
 
 static ssize_t platform_profile_choices_show(struct device *dev,
 					struct device_attribute *attr,
@@ -49,11 +67,8 @@ static ssize_t platform_profile_choices_show(struct device *dev,
 	return len;
 }
 
-static ssize_t platform_profile_show(struct device *dev,
-					struct device_attribute *attr,
-					char *buf)
+int platform_profile_get(enum platform_profile_option *profile)
 {
-	enum platform_profile_option profile = PLATFORM_PROFILE_BALANCED;
 	int err;
 
 	err = mutex_lock_interruptible(&profile_lock);
@@ -65,15 +80,28 @@ static ssize_t platform_profile_show(struct device *dev,
 		return -ENODEV;
 	}
 
-	err = cur_profile->profile_get(cur_profile, &profile);
+	err = cur_profile->profile_get(cur_profile, profile);
 	mutex_unlock(&profile_lock);
 	if (err)
 		return err;
 
 	/* Check that profile is valid index */
-	if (WARN_ON((profile < 0) || (profile >= ARRAY_SIZE(profile_names))))
+	if (WARN_ON((*profile < 0) || (*profile >= ARRAY_SIZE(profile_names))))
 		return -EIO;
 
+	return 0;
+}
+EXPORT_SYMBOL_GPL(platform_profile_get);
+
+static ssize_t platform_profile_show(struct device *dev,
+					struct device_attribute *attr,
+					char *buf)
+{
+	enum platform_profile_option profile = PLATFORM_PROFILE_BALANCED;
+	int ret = platform_profile_get(&profile);
+
+	if (ret)
+		return ret;
 	return sysfs_emit(buf, "%s\n", profile_names[profile]);
 }
 
@@ -106,8 +134,10 @@ static ssize_t platform_profile_store(struct device *dev,
 	}
 
 	err = cur_profile->profile_set(cur_profile, i);
-	if (!err)
+	if (!err) {
 		sysfs_notify(acpi_kobj, NULL, "platform_profile");
+		platform_profile_call_notifier(PLATFORM_PROFILE_CHANGED, &i);
+	}
 
 	mutex_unlock(&profile_lock);
 	if (err)
@@ -130,9 +160,17 @@ static const struct attribute_group platform_profile_group = {
 
 void platform_profile_notify(void)
 {
+	enum platform_profile_option profile;
+	int ret;
+
 	if (!cur_profile)
 		return;
 	sysfs_notify(acpi_kobj, NULL, "platform_profile");
+	ret = platform_profile_get(&profile);
+	if (ret)
+		return;
+	platform_profile_call_notifier(PLATFORM_PROFILE_CHANGED, &profile);
+
 }
 EXPORT_SYMBOL_GPL(platform_profile_notify);
 
diff --git a/include/linux/platform_profile.h b/include/linux/platform_profile.h
index a6329003aee7..dca9d47e18eb 100644
--- a/include/linux/platform_profile.h
+++ b/include/linux/platform_profile.h
@@ -11,6 +11,8 @@
 
 #include <linux/bitops.h>
 
+struct notifier_block;
+
 /*
  * If more options are added please update profile_names array in
  * platform_profile.c and sysfs-platform_profile documentation.
@@ -37,5 +39,13 @@ struct platform_profile_handler {
 int platform_profile_register(struct platform_profile_handler *pprof);
 int platform_profile_remove(void);
 void platform_profile_notify(void);
+int platform_profile_get(enum platform_profile_option *profile);
+
+int platform_profile_register_notifier(struct notifier_block *nb);
+int platform_profile_unregister_notifier(struct notifier_block *nb);
+
+enum platform_profile_notifier_actions {
+	PLATFORM_PROFILE_CHANGED,
+};
 
 #endif  /*_PLATFORM_PROFILE_H_*/
-- 
2.25.1