[PATCH v1 2/2] Revert "thermal: hwmon: Register a hwmon device for each thermal zone"

["Rafael J. Wysocki" <rafael@kernel.org>]

From: "Rafael J. Wysocki" <rafael.j.wysocki@intel.com>

Revert commit d6323469bcfb ("thermal: hwmon: Register a hwmon device
for each thermal zone") that changed the names of hwmon class devices
associated with thermal zones and their sysfs layout which made user
space unhappy.

Closes: https://lore.kernel.org/linux-pm/cafd8af9-c6e9-4bf2-b496-23e796fbc9a6@linux.dev/
Closes: https://lore.kernel.org/linux-hwmon/ab8b093b-46e6-4738-afcf-4b97c9ad5af9@googlemail.com/
Cc: stable@vger.kernel.org
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
---
 drivers/thermal/thermal_hwmon.c | 151 ++++++++++++++++++++++----------
 1 file changed, 104 insertions(+), 47 deletions(-)

diff --git a/drivers/thermal/thermal_hwmon.c b/drivers/thermal/thermal_hwmon.c
index 223ae1571655..597c33c8a555 100644
--- a/drivers/thermal/thermal_hwmon.c
+++ b/drivers/thermal/thermal_hwmon.c
@@ -19,33 +19,30 @@
 #include "thermal_hwmon.h"
 #include "thermal_core.h"
 
-/*
- * Needs to be large enough to hold a thermal zone type string followed by an
- * underline character and a 32-bit integer in decimal representation.
- */
-#define THERMAL_HWMON_NAME_LENGTH (THERMAL_NAME_LENGTH + 11)
+/* hwmon sys I/F */
+/* thermal zone devices with the same type share one hwmon device */
+struct thermal_hwmon_device {
+	char type[THERMAL_NAME_LENGTH];
+	struct device *device;
+	int count;
+	struct list_head tz_list;
+	struct list_head node;
+};
 
 struct thermal_hwmon_attr {
 	struct device_attribute attr;
+	char name[16];
 };
 
 /* one temperature input for each thermal zone */
 struct thermal_hwmon_temp {
+	struct list_head hwmon_node;
 	struct thermal_zone_device *tz;
 	struct thermal_hwmon_attr temp_input;	/* hwmon sys attr */
 	struct thermal_hwmon_attr temp_crit;	/* hwmon sys attr */
 	bool temp_crit_present;
 };
 
-/* hwmon sys I/F */
-/* thermal zone devices with the same type share one hwmon device */
-struct thermal_hwmon_device {
-	char name[THERMAL_HWMON_NAME_LENGTH];
-	struct device *device;
-	struct list_head node;
-	struct thermal_hwmon_temp tz_temp;
-};
-
 static LIST_HEAD(thermal_hwmon_list);
 
 static DEFINE_MUTEX(thermal_hwmon_list_lock);
@@ -91,6 +88,45 @@ temp_crit_show(struct device *dev, struct device_attribute *attr, char *buf)
 	return sysfs_emit(buf, "%d\n", temperature);
 }
 
+
+static struct thermal_hwmon_device *
+thermal_hwmon_lookup_by_type(const struct thermal_zone_device *tz)
+{
+	struct thermal_hwmon_device *hwmon;
+	char type[THERMAL_NAME_LENGTH];
+
+	mutex_lock(&thermal_hwmon_list_lock);
+	list_for_each_entry(hwmon, &thermal_hwmon_list, node) {
+		strscpy(type, tz->type);
+		strreplace(type, '-', '_');
+		if (!strcmp(hwmon->type, type)) {
+			mutex_unlock(&thermal_hwmon_list_lock);
+			return hwmon;
+		}
+	}
+	mutex_unlock(&thermal_hwmon_list_lock);
+
+	return NULL;
+}
+
+/* Find the temperature input matching a given thermal zone */
+static struct thermal_hwmon_temp *
+thermal_hwmon_lookup_temp(const struct thermal_hwmon_device *hwmon,
+			  const struct thermal_zone_device *tz)
+{
+	struct thermal_hwmon_temp *temp;
+
+	mutex_lock(&thermal_hwmon_list_lock);
+	list_for_each_entry(temp, &hwmon->tz_list, hwmon_node)
+		if (temp->tz == tz) {
+			mutex_unlock(&thermal_hwmon_list_lock);
+			return temp;
+		}
+	mutex_unlock(&thermal_hwmon_list_lock);
+
+	return NULL;
+}
+
 static bool thermal_zone_crit_temp_valid(struct thermal_zone_device *tz)
 {
 	int temp;
@@ -101,39 +137,54 @@ int thermal_add_hwmon_sysfs(struct thermal_zone_device *tz)
 {
 	struct thermal_hwmon_device *hwmon;
 	struct thermal_hwmon_temp *temp;
+	int new_hwmon_device = 1;
 	int result;
 
+	hwmon = thermal_hwmon_lookup_by_type(tz);
+	if (hwmon) {
+		new_hwmon_device = 0;
+		goto register_sys_interface;
+	}
+
 	hwmon = kzalloc_obj(*hwmon);
 	if (!hwmon)
 		return -ENOMEM;
 
-	/*
-	 * Append the thermal zone ID preceded by an underline character to the
-	 * type to disambiguate the sensors command output.
-	 */
-	scnprintf(hwmon->name, THERMAL_HWMON_NAME_LENGTH, "%s_%d", tz->type, tz->id);
-	strreplace(hwmon->name, '-', '_');
+	INIT_LIST_HEAD(&hwmon->tz_list);
+	strscpy(hwmon->type, tz->type, THERMAL_NAME_LENGTH);
+	strreplace(hwmon->type, '-', '_');
 	hwmon->device = hwmon_device_register_for_thermal(&tz->device,
-							  hwmon->name, hwmon);
+							  hwmon->type, hwmon);
 	if (IS_ERR(hwmon->device)) {
 		result = PTR_ERR(hwmon->device);
 		goto free_mem;
 	}
 
-	temp = &hwmon->tz_temp;
+ register_sys_interface:
+	temp = kzalloc_obj(*temp);
+	if (!temp) {
+		result = -ENOMEM;
+		goto unregister_name;
+	}
 
 	temp->tz = tz;
+	hwmon->count++;
 
-	temp->temp_input.attr.attr.name = "temp1_input";
+	snprintf(temp->temp_input.name, sizeof(temp->temp_input.name),
+		 "temp%d_input", hwmon->count);
+	temp->temp_input.attr.attr.name = temp->temp_input.name;
 	temp->temp_input.attr.attr.mode = 0444;
 	temp->temp_input.attr.show = temp_input_show;
 	sysfs_attr_init(&temp->temp_input.attr.attr);
 	result = device_create_file(hwmon->device, &temp->temp_input.attr);
 	if (result)
-		goto unregister_name;
+		goto free_temp_mem;
 
 	if (thermal_zone_crit_temp_valid(tz)) {
-		temp->temp_crit.attr.attr.name = "temp1_crit";
+		snprintf(temp->temp_crit.name,
+				sizeof(temp->temp_crit.name),
+				"temp%d_crit", hwmon->count);
+		temp->temp_crit.attr.attr.name = temp->temp_crit.name;
 		temp->temp_crit.attr.attr.mode = 0444;
 		temp->temp_crit.attr.show = temp_crit_show;
 		sysfs_attr_init(&temp->temp_crit.attr.attr);
@@ -145,17 +196,21 @@ int thermal_add_hwmon_sysfs(struct thermal_zone_device *tz)
 		temp->temp_crit_present = true;
 	}
 
-	/* The list is needed for hwmon lookup during removal. */
 	mutex_lock(&thermal_hwmon_list_lock);
-	list_add_tail(&hwmon->node, &thermal_hwmon_list);
+	if (new_hwmon_device)
+		list_add_tail(&hwmon->node, &thermal_hwmon_list);
+	list_add_tail(&temp->hwmon_node, &hwmon->tz_list);
 	mutex_unlock(&thermal_hwmon_list_lock);
 
 	return 0;
 
  unregister_input:
 	device_remove_file(hwmon->device, &temp->temp_input.attr);
+ free_temp_mem:
+	kfree(temp);
  unregister_name:
-	hwmon_device_unregister(hwmon->device);
+	if (new_hwmon_device)
+		hwmon_device_unregister(hwmon->device);
  free_mem:
 	kfree(hwmon);
 
@@ -163,37 +218,39 @@ int thermal_add_hwmon_sysfs(struct thermal_zone_device *tz)
 }
 EXPORT_SYMBOL_GPL(thermal_add_hwmon_sysfs);
 
-static struct thermal_hwmon_device *
-thermal_hwmon_lookup(const struct thermal_zone_device *tz)
-{
-	struct thermal_hwmon_device *hwmon;
-
-	list_for_each_entry(hwmon, &thermal_hwmon_list, node) {
-		if (hwmon->tz_temp.tz == tz)
-			return hwmon;
-	}
-	return NULL;
-}
-
 void thermal_remove_hwmon_sysfs(struct thermal_zone_device *tz)
 {
 	struct thermal_hwmon_device *hwmon;
 	struct thermal_hwmon_temp *temp;
 
-	scoped_guard(mutex, &thermal_hwmon_list_lock) {
-		hwmon = thermal_hwmon_lookup(tz);
-		if (!hwmon)
-			return;
-
-		list_del(&hwmon->node);
+	hwmon = thermal_hwmon_lookup_by_type(tz);
+	if (unlikely(!hwmon)) {
+		/* Should never happen... */
+		dev_dbg(&tz->device, "hwmon device lookup failed!\n");
+		return;
 	}
 
-	temp = &hwmon->tz_temp;
+	temp = thermal_hwmon_lookup_temp(hwmon, tz);
+	if (unlikely(!temp)) {
+		/* Should never happen... */
+		dev_dbg(&tz->device, "temperature input lookup failed!\n");
+		return;
+	}
 
 	device_remove_file(hwmon->device, &temp->temp_input.attr);
 	if (temp->temp_crit_present)
 		device_remove_file(hwmon->device, &temp->temp_crit.attr);
 
+	mutex_lock(&thermal_hwmon_list_lock);
+	list_del(&temp->hwmon_node);
+	kfree(temp);
+	if (!list_empty(&hwmon->tz_list)) {
+		mutex_unlock(&thermal_hwmon_list_lock);
+		return;
+	}
+	list_del(&hwmon->node);
+	mutex_unlock(&thermal_hwmon_list_lock);
+
 	hwmon_device_unregister(hwmon->device);
 	kfree(hwmon);
 }
-- 
2.51.0