--
Changed from v7
- removed set_freq from the common devfreq interface
- added get_devfreq, a mutex-protected wrapper for find_device_devfreq
(for sysfs interfaces and later with governor-support)
- corrected ABI documentation.

Changed from v6
- poling_interval is writable.

Changed from v5
- updated devferq_update usage.

Changed from v4
- removed system-wide sysfs interface
- removed tickling sysfs interface
- added set_freq for userspace governor (and any other governors that
 require user input)

Changed from v3
- corrected sysfs API usage
- corrected error messages
- moved sysfs entry location
- added sysfs entries

Changed from v2
- add ABI entries for devfreq sysfs interface
---
 Documentation/ABI/testing/sysfs-devices-power |   37 ++++++
 drivers/devfreq/devfreq.c                     |  150 +++++++++++++++++++++++++
 2 files changed, 187 insertions(+), 0 deletions(-)

diff --git a/Documentation/ABI/testing/sysfs-devices-power b/Documentation/ABI/testing/sysfs-devices-power
index 8ffbc25..57f4591 100644
--- a/Documentation/ABI/testing/sysfs-devices-power
+++ b/Documentation/ABI/testing/sysfs-devices-power

@@ -165,3 +165,40 @@ Description:

               Not all drivers support this attribute.  If it isn't supported,
               attempts to read or write it will yield I/O errors.
+
+What:          /sys/devices/.../power/devfreq_governor
+Date:          July 2011
+Contact:       MyungJoo Ham [off-list ref]
+Description:
+               The /sys/devices/.../power/devfreq_governor shows the name
+               of the governor used by the corresponding device.
+
+What:          /sys/devices/.../power/devfreq_cur_freq
+Date:          July 2011
+Contact:       MyungJoo Ham [off-list ref]
+Description:
+               The /sys/devices/.../power/devfreq_cur_freq shows the current
+               frequency of the corresponding device.
+
+What:          /sys/devices/.../power/devfreq_max_freq
+Date:          July 2011
+Contact:       MyungJoo Ham [off-list ref]
+Description:
+               The /sys/devices/.../power/devfreq_max_freq shows the
+               maximum operable frequency of the corresponding device.
+
+What:          /sys/devices/.../power/devfreq_min_freq
+Date:          July 2011
+Contact:       MyungJoo Ham [off-list ref]
+Description:
+               The /sys/devices/.../power/devfreq_min_freq shows the
+               minimum operable frequency of the corresponding device.
+
+What:          /sys/devices/.../power/devfreq_polling_interval
+Date:          July 2011
+Contact:       MyungJoo Ham [off-list ref]
+Description:
+               The /sys/devices/.../power/devfreq_polling_interval sets and
+               shows the requested polling interval of the corresponding
+               device. The values are represented in ms. If the value is less
+               than 1 jiffy, it is considered to be 0, which means no polling.

diff --git a/drivers/devfreq/devfreq.c b/drivers/devfreq/devfreq.c
index df63bdc..5bbece6 100644
--- a/drivers/devfreq/devfreq.c
+++ b/drivers/devfreq/devfreq.c

@@ -37,6 +37,8 @@ static struct delayed_work devfreq_work;

 static LIST_HEAD(devfreq_list);
 static DEFINE_MUTEX(devfreq_list_lock);

+static struct attribute_group dev_attr_group;
+
 /**
 * find_device_devfreq() - find devfreq struct using device pointer
 * @dev:       device pointer used to lookup device devfreq.

@@ -62,6 +64,22 @@ static struct devfreq *find_device_devfreq(struct device *dev)

 }

 /**
+ * get_devfreq() - find devfreq struct. a wrapped find_device_devfreq()
+ *             with mutex protection.
+ * @dev:       device pointer used to lookup device devfreq.
+ */
+static struct devfreq *get_devfreq(struct device *dev)
+{
+       struct devfreq *ret;
+
+       mutex_lock(&devfreq_list_lock);
+       ret = find_device_devfreq(dev);
+       mutex_unlock(&devfreq_list_lock);
+
+       return ret;
+}
+
+/**
 * devfreq_do() - Check the usage profile of a given device and configure
 *             frequency and voltage accordingly
 * @devfreq:   devfreq info of the given device

@@ -149,6 +167,8 @@ static void devfreq_monitor(struct work_struct *work)

                               dev_err(devfreq->dev, "Due to devfreq_do error(%d), devfreq(%s) is removed from the device\n",
                                       error, devfreq->governor->name);

+                               sysfs_unmerge_group(&devfreq->dev->kobj,
+                                                   &dev_attr_group);
                               list_del(&devfreq->node);
                               kfree(devfreq);

@@ -239,6 +259,8 @@ int devfreq_add_device(struct device *dev, struct devfreq_dev_profile *profile,

               queue_delayed_work(devfreq_wq, &devfreq_work,
                                  devfreq->next_polling);
       }
+
+       sysfs_merge_group(&dev->kobj, &dev_attr_group);
 out:
       mutex_unlock(&devfreq_list_lock);

@@ -271,6 +293,8 @@ int devfreq_remove_device(struct device *dev)

               goto out;
       }

+       sysfs_unmerge_group(&dev->kobj, &dev_attr_group);
+
       list_del(&devfreq->node);
       srcu_notifier_chain_unregister(nh, &devfreq->nb);
       kfree(devfreq);

@@ -279,6 +303,132 @@ out:

       return 0;
 }

+static ssize_t show_governor(struct device *dev,
+                            struct device_attribute *attr, char *buf)
+{
+       struct devfreq *df = get_devfreq(dev);
+
+       if (IS_ERR(df))
+               return PTR_ERR(df);
+       if (!df->governor)
+               return -EINVAL;
+
+       return sprintf(buf, "%s\n", df->governor->name);
+}
+
+static ssize_t show_freq(struct device *dev,
+                        struct device_attribute *attr, char *buf)
+{
+       struct devfreq *df = get_devfreq(dev);
+
+       if (IS_ERR(df))
+               return PTR_ERR(df);
+
+       return sprintf(buf, "%lu\n", df->previous_freq);
+}
+
+static ssize_t show_max_freq(struct device *dev,
+                            struct device_attribute *attr, char *buf)
+{
+       struct devfreq *df = get_devfreq(dev);
+       unsigned long freq = ULONG_MAX;
+       struct opp *opp;
+
+       if (IS_ERR(df))
+               return PTR_ERR(df);
+       if (!df->dev)
+               return -EINVAL;
+
+       opp = opp_find_freq_floor(df->dev, &freq);
+       if (IS_ERR(opp))
+               return PTR_ERR(opp);
+
+       return sprintf(buf, "%lu\n", freq);
+}
+
+static ssize_t show_min_freq(struct device *dev,
+                            struct device_attribute *attr, char *buf)
+{
+       struct devfreq *df = get_devfreq(dev);
+       unsigned long freq = 0;
+       struct opp *opp;
+
+       if (IS_ERR(df))
+               return PTR_ERR(df);
+       if (!df->dev)
+               return -EINVAL;
+
+       opp = opp_find_freq_ceil(df->dev, &freq);
+       if (IS_ERR(opp))
+               return PTR_ERR(opp);
+
+       return sprintf(buf, "%lu\n", freq);
+}
+
+static ssize_t show_polling_interval(struct device *dev,
+                                    struct device_attribute *attr, char *buf)
+{
+       struct devfreq *df = get_devfreq(dev);
+
+       if (IS_ERR(df))
+               return PTR_ERR(df);
+       if (!df->profile)
+               return -EINVAL;
+
+       return sprintf(buf, "%d\n", df->profile->polling_ms);
+}
+
+static ssize_t store_polling_interval(struct device *dev,
+                                     struct device_attribute *attr,
+                                     const char *buf, size_t count)
+{
+       struct devfreq *df = get_devfreq(dev);
+       unsigned int value;
+       int ret;
+
+       if (IS_ERR(df))
+               return PTR_ERR(df);
+       if (!df->profile)
+               return -EINVAL;
+
+       ret = sscanf(buf, "%u", &value);
+       if (ret != 1)
+               return -EINVAL;
+
+       df->profile->polling_ms = value;
+       df->next_polling = df->polling_jiffies
+                        = msecs_to_jiffies(value);
+
+       mutex_lock(&devfreq_list_lock);
+       if (df->next_polling > 0 && !polling) {
+               polling = true;
+               queue_delayed_work(devfreq_wq, &devfreq_work,
+                                  df->next_polling);
+       }
+       mutex_unlock(&devfreq_list_lock);
+
+       return count;
+}
+
+static DEVICE_ATTR(devfreq_governor, 0444, show_governor, NULL);
+static DEVICE_ATTR(devfreq_cur_freq, 0444, show_freq, NULL);
+static DEVICE_ATTR(devfreq_max_freq, 0444, show_max_freq, NULL);
+static DEVICE_ATTR(devfreq_min_freq, 0444, show_min_freq, NULL);
+static DEVICE_ATTR(devfreq_polling_interval, 0644, show_polling_interval,
+                  store_polling_interval);
+static struct attribute *dev_entries[] = {
+       &dev_attr_devfreq_governor.attr,
+       &dev_attr_devfreq_cur_freq.attr,
+       &dev_attr_devfreq_max_freq.attr,
+       &dev_attr_devfreq_min_freq.attr,
+       &dev_attr_devfreq_polling_interval.attr,
+       NULL,
+};
+static struct attribute_group dev_attr_group = {
+       .name   = power_group_name,
+       .attrs  = dev_entries,
+};
+
 /**
 * devfreq_init() - Initialize data structure for devfreq framework and
 *               start polling registered devfreq devices.
--
1.7.4.1