thermal: netlink: Fix compilation error when CONFIG_NET=n

When the network is not configured, the netlink is disabled on all
the system. The thermal framework assumed the netlink is always
opt-in.

Fix this by adding a Kconfig option for the netlink notification,
defaulting to yes and depending on CONFIG_NET.

As the change implies multiple stubs and in order to not pollute the
internal thermal header, the thermal_nelink.h has been added and
included in the thermal_core.h, so this one regain some kind of
clarity.

Reported-by: Randy Dunlap <rdunlap@infradead.org>
Signed-off-by: Daniel Lezcano <daniel.lezcano@linaro.org>
Reviewed-by: Amit Kucheria <amit.kucheria@linaro.org>
Link: https://lore.kernel.org/r/20200707090159.1018-1-daniel.lezcano@linaro.org

drivers/thermal/Kconfig

@@ -17,6 +17,16 @@ menuconfig THERMAL
 
 if THERMAL
 
+config THERMAL_NETLINK
+	bool "Thermal netlink management"
+	depends on NET
+	default y
+	help
+	  The thermal framework has a netlink interface to do thermal
+	  zones discovery, temperature readings and events such as
+	  trip point crossed, cooling device update or governor
+	  change. It is recommended to enable the feature.
+
 config THERMAL_STATISTICS
 	bool "Thermal state transition statistics"
 	help

drivers/thermal/Makefile

@@ -5,7 +5,10 @@
 
 obj-$(CONFIG_THERMAL)		+= thermal_sys.o
 thermal_sys-y			+= thermal_core.o thermal_sysfs.o \
-					thermal_helpers.o thermal_netlink.o
+					thermal_helpers.o
+
+# netlink interface to manage the thermal framework
+thermal_sys-$(CONFIG_THERMAL_NETLINK)		+= thermal_netlink.o
 
 # interface to/from other layers providing sensors
 thermal_sys-$(CONFIG_THERMAL_HWMON)		+= thermal_hwmon.o

drivers/thermal/thermal_core.h

@@ -12,6 +12,8 @@
 #include <linux/device.h>
 #include <linux/thermal.h>
 
+#include "thermal_netlink.h"
+
 /* Default Thermal Governor */
 #if defined(CONFIG_THERMAL_DEFAULT_GOV_STEP_WISE)
 #define DEFAULT_THERMAL_GOVERNOR       "step_wise"
@@ -52,24 +54,6 @@ int for_each_thermal_governor(int (*cb)(struct thermal_governor *, void *),
 
 struct thermal_zone_device *thermal_zone_get_by_id(int id);
 
-/* Netlink notification function */
-int thermal_notify_tz_create(int tz_id, const char *name);
-int thermal_notify_tz_delete(int tz_id);
-int thermal_notify_tz_enable(int tz_id);
-int thermal_notify_tz_disable(int tz_id);
-int thermal_notify_tz_trip_down(int tz_id, int id);
-int thermal_notify_tz_trip_up(int tz_id, int id);
-int thermal_notify_tz_trip_delete(int tz_id, int id);
-int thermal_notify_tz_trip_add(int tz_id, int id, int type,
-			       int temp, int hyst);
-int thermal_notify_tz_trip_change(int tz_id, int id, int type,
-				  int temp, int hyst);
-int thermal_notify_cdev_state_update(int cdev_id, int state);
-int thermal_notify_cdev_add(int cdev_id, const char *name, int max_state);
-int thermal_notify_cdev_delete(int cdev_id);
-int thermal_notify_tz_gov_change(int tz_id, const char *name);
-int thermal_genl_sampling_temp(int id, int temp);
-
 struct thermal_attr {
 	struct device_attribute attr;
 	char name[THERMAL_NAME_LENGTH];

drivers/thermal/thermal_netlink.h

@@ -0,0 +1,98 @@
+/* SPDX-License-Identifier: GPL-2.0 */
+/*
+ *  Copyright (C) Linaro Ltd 2020
+ *  Author: Daniel Lezcano <daniel.lezcano@linaro.org>
+ */
+
+/* Netlink notification function */
+#ifdef CONFIG_THERMAL_NETLINK
+int thermal_notify_tz_create(int tz_id, const char *name);
+int thermal_notify_tz_delete(int tz_id);
+int thermal_notify_tz_enable(int tz_id);
+int thermal_notify_tz_disable(int tz_id);
+int thermal_notify_tz_trip_down(int tz_id, int id);
+int thermal_notify_tz_trip_up(int tz_id, int id);
+int thermal_notify_tz_trip_delete(int tz_id, int id);
+int thermal_notify_tz_trip_add(int tz_id, int id, int type,
+			       int temp, int hyst);
+int thermal_notify_tz_trip_change(int tz_id, int id, int type,
+				  int temp, int hyst);
+int thermal_notify_cdev_state_update(int cdev_id, int state);
+int thermal_notify_cdev_add(int cdev_id, const char *name, int max_state);
+int thermal_notify_cdev_delete(int cdev_id);
+int thermal_notify_tz_gov_change(int tz_id, const char *name);
+int thermal_genl_sampling_temp(int id, int temp);
+#else
+static inline int thermal_notify_tz_create(int tz_id, const char *name)
+{
+	return 0;
+}
+
+static inline int thermal_notify_tz_delete(int tz_id)
+{
+	return 0;
+}
+
+static inline int thermal_notify_tz_enable(int tz_id)
+{
+	return 0;
+}
+
+static inline int thermal_notify_tz_disable(int tz_id)
+{
+	return 0;
+}
+
+static inline int thermal_notify_tz_trip_down(int tz_id, int id)
+{
+	return 0;
+}
+
+static inline int thermal_notify_tz_trip_up(int tz_id, int id)
+{
+	return 0;
+}
+
+static inline int thermal_notify_tz_trip_delete(int tz_id, int id)
+{
+	return 0;
+}
+
+static inline int thermal_notify_tz_trip_add(int tz_id, int id, int type,
+					     int temp, int hyst)
+{
+	return 0;
+}
+
+static inline int thermal_notify_tz_trip_change(int tz_id, int id, int type,
+						int temp, int hyst)
+{
+	return 0;
+}
+
+static inline int thermal_notify_cdev_state_update(int cdev_id, int state)
+{
+	return 0;
+}
+
+static inline int thermal_notify_cdev_add(int cdev_id, const char *name,
+					  int max_state)
+{
+	return 0;
+}
+
+static inline int thermal_notify_cdev_delete(int cdev_id)
+{
+	return 0;
+}
+
+static inline int thermal_notify_tz_gov_change(int tz_id, const char *name)
+{
+	return 0;
+}
+
+static inline int thermal_genl_sampling_temp(int id, int temp)
+{
+	return 0;
+}
+#endif /* CONFIG_THERMAL_NETLINK */