[PATCH v2 14/15] ACPI: platform_profile: Allow multiple handlers

[Mario Limonciello <mario.limonciello@amd.com>]

Multiple drivers may attempt to register platform profile handlers,
but only one may be registered and the behavior is non-deterministic
for which one wins.  It's mostly controlled by probing order.

This can be problematic if one driver changes CPU settings and another
driver notifies the EC for changing fan curves.

Modify the ACPI platform profile handler to let multiple drivers
register platform profile handlers and abstract this detail from userspace.

To avoid undefined behaviors only offer profiles that are commonly
advertised across multiple handlers.

If any problems occur when changing profiles for any driver, then revert
back to the balanced profile, which is now required.

Tested-by: Matthew Schwartz <matthew.schwartz@linux.dev>
Signed-off-by: Mario Limonciello <mario.limonciello@amd.com>
---
 drivers/acpi/platform_profile.c | 19 ++++++++-----------
 1 file changed, 8 insertions(+), 11 deletions(-)

diff --git a/drivers/acpi/platform_profile.c b/drivers/acpi/platform_profile.c
index e6ea5b600e2af..2794a8f686200 100644
--- a/drivers/acpi/platform_profile.c
+++ b/drivers/acpi/platform_profile.c
@@ -9,7 +9,6 @@
 #include <linux/platform_profile.h>
 #include <linux/sysfs.h>
 
-static struct platform_profile_handler *cur_profile;
 static LIST_HEAD(platform_profile_handler_list);
 static DEFINE_MUTEX(profile_lock);
 
@@ -188,7 +187,8 @@ static const struct attribute_group platform_profile_group = {
 
 void platform_profile_notify(void)
 {
-	if (!cur_profile)
+	guard(mutex)(&profile_lock);
+	if (!platform_profile_is_registered())
 		return;
 	sysfs_notify(acpi_kobj, NULL, "platform_profile");
 }
@@ -251,17 +251,15 @@ int platform_profile_register(struct platform_profile_handler *pprof)
 	}
 
 	guard(mutex)(&profile_lock);
-	/* We can only have one active profile */
-	if (cur_profile)
-		return -EEXIST;
 
-	err = sysfs_create_group(acpi_kobj, &platform_profile_group);
-	if (err)
-		return err;
+	if (!platform_profile_is_registered()) {
+		err = sysfs_create_group(acpi_kobj, &platform_profile_group);
+		if (err)
+			return err;
+	}
 	list_add_tail(&pprof->list, &platform_profile_handler_list);
 	sysfs_notify(acpi_kobj, NULL, "platform_profile");
 
-	cur_profile = pprof;
 	return 0;
 }
 EXPORT_SYMBOL_GPL(platform_profile_register);
@@ -272,9 +270,8 @@ int platform_profile_remove(struct platform_profile_handler *pprof)
 
 	list_del(&pprof->list);
 
-	cur_profile = NULL;
-
 	sysfs_notify(acpi_kobj, NULL, "platform_profile");
+
 	if (!platform_profile_is_registered())
 		sysfs_remove_group(acpi_kobj, &platform_profile_group);
 
-- 
2.43.0