[PATCH v2] devfreq: governor: Add a private governor_data for governors in devfreq

[Kant Fan]

The member void *data in the structure devfreq can be overwrite
by governor_userspace. For example:
1. The device driver assigned the devfreq governor to simple_ondemand
by the function devfreq_add_device() and init the devfreq member
void *data to a pointer of a static structure devfreq_simple_ondemand_data
by the function devfreq_add_device().
2. The user changed the devfreq governor to userspace by the command
"echo userspace > /sys/class/devfreq/.../governor".
3. The governor userspace alloced a dynamic memory for the struct
userspace_data and assigend the member void *data of devfreq to
this memory by the function userspace_init().
4. The user changed the devfreq governor back to simple_ondemand
by the command "echo simple_ondemand > /sys/class/devfreq/.../governor".
5. The governor userspace exited and assigned the member void *data
in the structure devfreq to NULL by the function userspace_exit().
6. The governor simple_ondemand fetched the static information of
devfreq_simple_ondemand_data in the function
devfreq_simple_ondemand_func() but the member void *data of devfreq was
assigned to NULL by the function userspace_exit().
7. The information of upthreshold and downdifferential is lost
and the governor simple_ondemand can't work correctly.

The member void *data in the structure devfreq is designed for
a static pointer used in a governor and inited by the function
devfreq_add_device(). This patch add an element named governor_data
in the devfreq structure which can be used by a governor(E.g userspace)
who want to assign a private data to do some private things.

Acked-by: MyungJoo Ham <myungjoo.ham@xxxxxxxxxxx>

Signed-off-by: Kant Fan <kant@xxxxxxxxxxxxxxxxx>
---
 drivers/devfreq/governor_userspace.c | 12 ++++++------
 include/linux/devfreq.h              |  7 ++++---
 2 files changed, 10 insertions(+), 9 deletions(-)

diff --git a/drivers/devfreq/governor_userspace.c b/drivers/devfreq/governor_userspace.c
index ab9db7adb3ad..d69672ccacc4 100644
--- a/drivers/devfreq/governor_userspace.c
+++ b/drivers/devfreq/governor_userspace.c
@@ -21,7 +21,7 @@ struct userspace_data {
 
 static int devfreq_userspace_func(struct devfreq *df, unsigned long *freq)
 {
-	struct userspace_data *data = df->data;
+	struct userspace_data *data = df->governor_data;
 
 	if (data->valid)
 		*freq = data->user_frequency;
@@ -40,7 +40,7 @@ static ssize_t set_freq_store(struct device *dev, struct device_attribute *attr,
 	int err = 0;
 
 	mutex_lock(&devfreq->lock);
-	data = devfreq->data;
+	data = devfreq->governor_data;
 
 	sscanf(buf, "%lu", &wanted);
 	data->user_frequency = wanted;
@@ -60,7 +60,7 @@ static ssize_t set_freq_show(struct device *dev,
 	int err = 0;
 
 	mutex_lock(&devfreq->lock);
-	data = devfreq->data;
+	data = devfreq->governor_data;
 
 	if (data->valid)
 		err = sprintf(buf, "%lu\n", data->user_frequency);
@@ -91,7 +91,7 @@ static int userspace_init(struct devfreq *devfreq)
 		goto out;
 	}
 	data->valid = false;
-	devfreq->data = data;
+	devfreq->governor_data = data;
 
 	err = sysfs_create_group(&devfreq->dev.kobj, &dev_attr_group);
 out:
@@ -107,8 +107,8 @@ static void userspace_exit(struct devfreq *devfreq)
 	if (devfreq->dev.kobj.sd)
 		sysfs_remove_group(&devfreq->dev.kobj, &dev_attr_group);
 
-	kfree(devfreq->data);
-	devfreq->data = NULL;
+	kfree(devfreq->governor_data);
+	devfreq->governor_data = NULL;
 }
 
 static int devfreq_userspace_handler(struct devfreq *devfreq,
diff --git a/include/linux/devfreq.h b/include/linux/devfreq.h
index 34aab4dd336c..d265af3fb0a4 100644
--- a/include/linux/devfreq.h
+++ b/include/linux/devfreq.h
@@ -152,8 +152,8 @@ struct devfreq_stats {
  * @max_state:		count of entry present in the frequency table.
  * @previous_freq:	previously configured frequency value.
  * @last_status:	devfreq user device info, performance statistics
- * @data:	Private data of the governor. The devfreq framework does not
- *		touch this.
+ * @data:	devfreq core pass to governors, governor should not change it.
+ * @governor_data:	private data for governors, devfreq core doesn't touch it.
  * @user_min_freq_req:	PM QoS minimum frequency request from user (via sysfs)
  * @user_max_freq_req:	PM QoS maximum frequency request from user (via sysfs)
  * @scaling_min_freq:	Limit minimum frequency requested by OPP interface
@@ -193,7 +193,8 @@ struct devfreq {
 	unsigned long previous_freq;
 	struct devfreq_dev_status last_status;
 
-	void *data; /* private data for governors */
+	void *data;
+	void *governor_data;
 
 	struct dev_pm_qos_request user_min_freq_req;
 	struct dev_pm_qos_request user_max_freq_req;
-- 
2.29.0