This patch adds notification support for those clients of cpu_cooling
APIs which may want to do something interesting after receiving these
cpu_cooling events. The notifier structure passed is of both Set/Get type.
The notfications events can be of type,
1. CPU_COOLING_SET_STATE_PRE
2. CPU_COOLING_SET_STATE_POST
3. CPU_COOLING_GET_CUR_STATE
4. CPU_COOLING_GET_MAX_STATE

The advantages of these notfications is to differentiate between different
P states in the cpufreq table and the cooling states. The clients of these
events may group few P states into 1 cooling states. Also some more cooling
states can be enabled when the maximum of P state is reached. Post notifications
can be used for those cases.

Signed-off-by: Amit Daniel Kachhap <redacted>
---
 drivers/thermal/cpu_cooling.c |   99 +++++++++++++++++++++++++++++++++++++++-
 include/linux/cpu_cooling.h   |   55 +++++++++++++++++++++++
 2 files changed, 151 insertions(+), 3 deletions(-)

diff --git a/drivers/thermal/cpu_cooling.c b/drivers/thermal/cpu_cooling.c
index 21f44d4..e2aeb36 100644
--- a/drivers/thermal/cpu_cooling.c
+++ b/drivers/thermal/cpu_cooling.c

@@ -50,6 +50,7 @@ struct cpufreq_cooling_device {
 	unsigned int cpufreq_state;
 	unsigned int cpufreq_val;
 	struct cpumask allowed_cpus;
+	struct cpufreq_cooling_status request_status;
 	struct list_head node;
 };
 static DEFINE_IDR(cpufreq_idr);

@@ -59,6 +60,8 @@ static DEFINE_MUTEX(cooling_cpufreq_lock);
 #define NOTIFY_INVALID NULL
 static struct cpufreq_cooling_device *notify_device;
 
+/* Notfier list to validates/updates the cpufreq cooling states */
+static BLOCKING_NOTIFIER_HEAD(cpufreq_cooling_state_notifier_list);
 /* A list to hold all the cpufreq cooling devices registered */
 static LIST_HEAD(cpufreq_cooling_list);
 

@@ -266,6 +269,21 @@ static unsigned int get_cpu_frequency(unsigned int cpu, unsigned long level)
 	return freq;
 }
 
+static int
+cpufreq_cooling_notify_states(struct cpufreq_cooling_status *request,
+			enum cpu_cooling_state_ops op)
+{
+	/* Invoke the notifiers which have registered for this state change */
+	if (op == CPU_COOLING_SET_STATE_PRE ||
+		op == CPU_COOLING_SET_STATE_POST ||
+		op == CPU_COOLING_GET_MAX_STATE ||
+		op == CPU_COOLING_GET_CUR_STATE) {
+		blocking_notifier_call_chain(
+			&cpufreq_cooling_state_notifier_list, op, request);
+	}
+	return 0;
+}
+
 /**
  * cpufreq_apply_cooling - function to apply frequency clipping.
  * @cpufreq_device: cpufreq_cooling_device pointer containing frequency

@@ -285,9 +303,18 @@ static int cpufreq_apply_cooling(struct cpufreq_cooling_device *cpufreq_device,
 	struct cpumask *mask = &cpufreq_device->allowed_cpus;
 	unsigned int cpu = cpumask_any(mask);
 
+	cpufreq_device->request_status.cur_state =
+						cpufreq_device->cpufreq_state;
+	cpufreq_device->request_status.new_state = cooling_state;
+
+	cpufreq_cooling_notify_states(&cpufreq_device->request_status,
+					CPU_COOLING_SET_STATE_PRE);
+
+	cooling_state = cpufreq_device->request_status.new_state;
 
 	/* Check if the old cooling action is same as new cooling action */
-	if (cpufreq_device->cpufreq_state == cooling_state)
+	if (cpufreq_device->cpufreq_state ==
+				cpufreq_device->request_status.new_state)
 		return 0;
 
 	clip_freq = get_cpu_frequency(cpu, cooling_state);

@@ -304,7 +331,8 @@ static int cpufreq_apply_cooling(struct cpufreq_cooling_device *cpufreq_device,
 	}
 
 	notify_device = NOTIFY_INVALID;
-
+	cpufreq_cooling_notify_states(&cpufreq_device->request_status,
+					CPU_COOLING_SET_STATE_POST);
 	return 0;
 }
 

@@ -383,6 +411,11 @@ static int cpufreq_get_max_state(struct thermal_cooling_device *cdev,
 	if (count > 0)
 		*state = count;
 
+	cpufreq_device->request_status.max_state = count;
+	cpufreq_cooling_notify_states(&cpufreq_device->request_status,
+					CPU_COOLING_GET_MAX_STATE);
+	*state = cpufreq_device->request_status.max_state;
+