ACPI: platform_profile: Allow multiple handlers

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 the
drivers that were already changed remain changed and the legacy sysfs
handler will report 'custom'.

Tested-by: Mark Pearson <[email protected]>
Tested-by: Matthew Schwartz <[email protected]>
Reviewed-by: Mark Pearson <[email protected]>
Reviewed-by: Armin Wolf <[email protected]>
Reviewed-by: Ilpo Järvinen <[email protected]>
Signed-off-by: Mario Limonciello <[email protected]>
Link: https://lore.kernel.org/r/[email protected]
Signed-off-by: Ilpo Järvinen <[email protected]>

Author: superm1

drivers/acpi/platform_profile.c

@@ -10,7 +10,6 @@
 #include <linux/platform_profile.h>
 #include <linux/sysfs.h>
 
-static struct platform_profile_handler *cur_profile;
 static DEFINE_MUTEX(profile_lock);
 
 static const char * const profile_names[] = {
@@ -410,8 +409,6 @@ static const struct attribute_group platform_profile_group = {
 
 void platform_profile_notify(struct platform_profile_handler *pprof)
 {
-	if (!cur_profile)
-		return;
 	scoped_cond_guard(mutex_intr, return, &profile_lock) {
 		_notify_class_profile(pprof->class_dev, NULL);
 	}
@@ -474,9 +471,6 @@ 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;
 
 	/* create class interface for individual handler */
 	pprof->minor = ida_alloc(&platform_profile_ida, GFP_KERNEL);
@@ -492,16 +486,13 @@ int platform_profile_register(struct platform_profile_handler *pprof)
 
 	sysfs_notify(acpi_kobj, NULL, "platform_profile");
 
-	cur_profile = pprof;
-
 	err = sysfs_update_group(acpi_kobj, &platform_profile_group);
 	if (err)
 		goto cleanup_cur;
 
 	return 0;
 
 cleanup_cur:
-	cur_profile = NULL;
 	device_unregister(pprof->class_dev);
 
 cleanup_ida:
@@ -516,8 +507,6 @@ int platform_profile_remove(struct platform_profile_handler *pprof)
 	int id;
 	guard(mutex)(&profile_lock);
 
-	cur_profile = NULL;
-
 	id = pprof->minor;
 	device_unregister(pprof->class_dev);
 	ida_free(&platform_profile_ida, id);