thermal/drivers/core: Use a char pointer for the cooling device name

We want to have any kind of name for the cooling devices as we do no
longer want to rely on auto-numbering. Let's replace the cooling
device's fixed array by a char pointer to be allocated dynamically
when registering the cooling device, so we don't limit the length of
the name.

Rework the error path at the same time as we have to rollback the
allocations in case of error.

Tested with a dummy device having the name:
 "Llanfairpwllgwyngyllgogerychwyrndrobwllllantysiliogogogoch"

A village on the island of Anglesey (Wales), known to have the longest
name in Europe.
Signed-off-by: NDaniel Lezcano <daniel.lezcano@linaro.org>
Reviewed-by: NLukasz Luba <lukasz.luba@arm.com>
Tested-by: NIdo Schimmel <idosch@nvidia.com>
Link: https://lore.kernel.org/r/20210314111333.16551-1-daniel.lezcano@linaro.org

drivers/net/ethernet/mellanox/mlxsw/core_thermal.c

@@ -141,7 +141,7 @@ static int mlxsw_get_cooling_device_idx(struct mlxsw_thermal *thermal,
 	/* Allow mlxsw thermal zone binding to an external cooling device */
 	for (i = 0; i < ARRAY_SIZE(mlxsw_thermal_external_allowed_cdev); i++) {
 		if (strnstr(cdev->type, mlxsw_thermal_external_allowed_cdev[i],
-			    sizeof(cdev->type)))
+			    strlen(cdev->type)))
 			return 0;
 	}
 

drivers/thermal/thermal_core.c

@@ -960,10 +960,7 @@ __thermal_cooling_device_register(struct device_node *np,
 {
 	struct thermal_cooling_device *cdev;
 	struct thermal_zone_device *pos = NULL;
-	int result;
-
-	if (type && strlen(type) >= THERMAL_NAME_LENGTH)
-		return ERR_PTR(-EINVAL);
+	int ret;
 
 	if (!ops || !ops->get_max_state || !ops->get_cur_state ||
 	    !ops->set_cur_state)
@@ -973,14 +970,17 @@ __thermal_cooling_device_register(struct device_node *np,
 	if (!cdev)
 		return ERR_PTR(-ENOMEM);
 
-	result = ida_simple_get(&thermal_cdev_ida, 0, 0, GFP_KERNEL);
-	if (result < 0) {
-		kfree(cdev);
-		return ERR_PTR(result);
+	ret = ida_simple_get(&thermal_cdev_ida, 0, 0, GFP_KERNEL);
+	if (ret < 0)
+		goto out_kfree_cdev;
+	cdev->id = ret;
+
+	cdev->type = kstrdup(type ? type : "", GFP_KERNEL);
+	if (!cdev->type) {
+		ret = -ENOMEM;
+		goto out_ida_remove;
 	}
 
-	cdev->id = result;
-	strlcpy(cdev->type, type ? : "", sizeof(cdev->type));
 	mutex_init(&cdev->lock);
 	INIT_LIST_HEAD(&cdev->thermal_instances);
 	cdev->np = np;
@@ -990,12 +990,9 @@ __thermal_cooling_device_register(struct device_node *np,
 	cdev->devdata = devdata;
 	thermal_cooling_device_setup_sysfs(cdev);
 	dev_set_name(&cdev->device, "cooling_device%d", cdev->id);
-	result = device_register(&cdev->device);
-	if (result) {
-		ida_simple_remove(&thermal_cdev_ida, cdev->id);
-		put_device(&cdev->device);
-		return ERR_PTR(result);
-	}
+	ret = device_register(&cdev->device);
+	if (ret)
+		goto out_kfree_type;
 
 	/* Add 'this' new cdev to the global cdev list */
 	mutex_lock(&thermal_list_lock);
@@ -1013,6 +1010,14 @@ __thermal_cooling_device_register(struct device_node *np,
 	mutex_unlock(&thermal_list_lock);
 
 	return cdev;
+
+out_kfree_type:
+	kfree(cdev->type);
+	put_device(&cdev->device);
+out_ida_remove:
+	ida_simple_remove(&thermal_cdev_ida, cdev->id);
+out_kfree_cdev:
+	return ERR_PTR(ret);
 }
 
 /**
@@ -1171,6 +1176,7 @@ void thermal_cooling_device_unregister(struct thermal_cooling_device *cdev)
 	ida_simple_remove(&thermal_cdev_ida, cdev->id);
 	device_del(&cdev->device);
 	thermal_cooling_device_destroy_sysfs(cdev);
+	kfree(cdev->type);
 	put_device(&cdev->device);
 }
 EXPORT_SYMBOL_GPL(thermal_cooling_device_unregister);

include/linux/thermal.h

@@ -91,7 +91,7 @@ struct thermal_cooling_device_ops {
 
 struct thermal_cooling_device {
 	int id;
-	char type[THERMAL_NAME_LENGTH];
+	char *type;
 	struct device device;
 	struct device_node *np;
 	void *devdata;