PM / QoS: Make it possible to expose device latency tolerance to userspace

Typically when a device is created the bus core it belongs to (for example
PCI) does not know if the device supports things like latency tolerance.
This is left to the driver that binds to the device in question. However,
at that time the device has already been created and there is no way to set
its dev->power.set_latency_tolerance anymore.

So follow what has been done for other PM QoS attributes as well and allow
drivers to expose and hide latency tolerance from userspace, if the device
supports it.

Acked-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
Signed-off-by: Mika Westerberg <mika.westerberg@linux.intel.com>
Signed-off-by: Andy Shevchenko <andriy.shevchenko@linux.intel.com>
Signed-off-by: Lee Jones <lee.jones@linaro.org>
diff --git a/include/linux/pm_qos.h b/include/linux/pm_qos.h
index 7b3ae0c..0f65d36 100644
--- a/include/linux/pm_qos.h
+++ b/include/linux/pm_qos.h
@@ -161,6 +161,8 @@
 int dev_pm_qos_update_flags(struct device *dev, s32 mask, bool set);
 s32 dev_pm_qos_get_user_latency_tolerance(struct device *dev);
 int dev_pm_qos_update_user_latency_tolerance(struct device *dev, s32 val);
+int dev_pm_qos_expose_latency_tolerance(struct device *dev);
+void dev_pm_qos_hide_latency_tolerance(struct device *dev);
 
 static inline s32 dev_pm_qos_requested_resume_latency(struct device *dev)
 {
@@ -229,6 +231,9 @@
 			{ return PM_QOS_LATENCY_TOLERANCE_NO_CONSTRAINT; }
 static inline int dev_pm_qos_update_user_latency_tolerance(struct device *dev, s32 val)
 			{ return 0; }
+static inline int dev_pm_qos_expose_latency_tolerance(struct device *dev)
+			{ return 0; }
+static inline void dev_pm_qos_hide_latency_tolerance(struct device *dev) {}
 
 static inline s32 dev_pm_qos_requested_resume_latency(struct device *dev) { return 0; }
 static inline s32 dev_pm_qos_requested_flags(struct device *dev) { return 0; }