PowerCap: Add class driver

The power capping framework providing a consistent interface between the
kernel and user space that allows power capping drivers to expose their
settings to user space in a uniform way.
The overall design of the framework is described in the documentation
added by the previous patch in this series.

Signed-off-by: Srinivas Pandruvada <srinivas.pandruvada@linux.intel.com>
Signed-off-by: Jacob Pan <jacob.jun.pan@linux.intel.com>
Reviewed-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>

3 files changed, 703 insertions, 0 deletions

diff --git a/drivers/powercap/Kconfig b/drivers/powercap/Kconfig
new file mode 100644
index 000000000000..a37055eb5ebc
--- /dev/null
+++ b/drivers/powercap/Kconfig
@@ -0,0 +1,19 @@
+#
+# Generic power capping sysfs interface configuration
+#
+
+menuconfig POWERCAP
+        bool "Generic powercap sysfs driver"
+        help
+          The power capping sysfs interface allows kernel subsystems to expose power
+          capping settings to user space in a consistent way.  Usually, it consists
+          of multiple control types that determine which settings may be exposed and
+          power zones representing parts of the system that can be subject to power
+          capping.
+
+          If you want this code to be compiled in, say Y here.
+
+if POWERCAP
+# Client driver configurations go here.
+
+endif
diff --git a/drivers/powercap/Makefile b/drivers/powercap/Makefile
new file mode 100644
index 000000000000..6defbc8dc4bf
--- /dev/null
+++ b/drivers/powercap/Makefile
@@ -0,0 +1 @@
+obj-$(CONFIG_POWERCAP)  += powercap_sys.o
diff --git a/drivers/powercap/powercap_sys.c b/drivers/powercap/powercap_sys.c
new file mode 100644
index 000000000000..c22fa4c78eaa
--- /dev/null
+++ b/drivers/powercap/powercap_sys.c
@@ -0,0 +1,683 @@
+/*
+ * Power capping class
+ * Copyright (c) 2013, Intel Corporation.
+ *
+ * This program is free software; you can redistribute it and/or modify it
+ * under the terms and conditions of the GNU General Public License,
+ * version 2, as published by the Free Software Foundation.
+ *
+ * This program is distributed in the hope it will be useful, but WITHOUT
+ * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
+ * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License for
+ * more details.
+ *
+ * You should have received a copy of the GNU General Public License along with
+ * this program; if not, write to the Free Software Foundation, Inc.
+ *
+ */
+
+#include <linux/module.h>
+#include <linux/device.h>
+#include <linux/err.h>
+#include <linux/slab.h>
+#include <linux/powercap.h>
+
+#define to_powercap_zone(n) container_of(n, struct powercap_zone, dev)
+#define to_powercap_control_type(n) \
+                        container_of(n, struct powercap_control_type, dev)
+
+/* Power zone show function */
+#define define_power_zone_show(_attr)           \
+static ssize_t _attr##_show(struct device *dev, \
+                                        struct device_attribute *dev_attr,\
+                                        char *buf) \
+{ \
+        u64 value; \
+        ssize_t len = -EINVAL; \
+        struct powercap_zone *power_zone = to_powercap_zone(dev); \
+        \
+        if (power_zone->ops->get_##_attr) { \
+                if (!power_zone->ops->get_##_attr(power_zone, &value)) \
+                        len = sprintf(buf, "%lld\n", value); \
+        } \
+        \
+        return len; \
+}
+
+/* The only meaningful input is 0 (reset), others are silently ignored */
+#define define_power_zone_store(_attr)          \
+static ssize_t _attr##_store(struct device *dev,\
+                                struct device_attribute *dev_attr, \
+                                const char *buf, size_t count) \
+{ \
+        int err; \
+        struct powercap_zone *power_zone = to_powercap_zone(dev); \
+        u64 value; \
+        \
+        err = kstrtoull(buf, 10, &value); \
+        if (err) \
+                return -EINVAL; \
+        if (value) \
+                return count; \
+        if (power_zone->ops->reset_##_attr) { \
+                if (!power_zone->ops->reset_##_attr(power_zone)) \
+                        return count; \
+        } \
+        \
+        return -EINVAL; \
+}
+
+/* Power zone constraint show function */
+#define define_power_zone_constraint_show(_attr) \
+static ssize_t show_constraint_##_attr(struct device *dev, \
+                                struct device_attribute *dev_attr,\
+                                char *buf) \
+{ \
+        u64 value; \
+        ssize_t len = -ENODATA; \
+        struct powercap_zone *power_zone = to_powercap_zone(dev); \
+        int id; \
+        struct powercap_zone_constraint *pconst;\
+        \
+        if (!sscanf(dev_attr->attr.name, "constraint_%d_", &id)) \
+                return -EINVAL; \
+        if (id >= power_zone->const_id_cnt)     \
+                return -EINVAL; \
+        pconst = &power_zone->constraints[id]; \
+        if (pconst && pconst->ops && pconst->ops->get_##_attr) { \
+                if (!pconst->ops->get_##_attr(power_zone, id, &value)) \
+                        len = sprintf(buf, "%lld\n", value); \
+        } \
+        \
+        return len; \
+}
+
+/* Power zone constraint store function */
+#define define_power_zone_constraint_store(_attr) \
+static ssize_t store_constraint_##_attr(struct device *dev,\
+                                struct device_attribute *dev_attr, \
+                                const char *buf, size_t count) \
+{ \
+        int err; \
+        u64 value; \
+        struct powercap_zone *power_zone = to_powercap_zone(dev); \
+        int id; \
+        struct powercap_zone_constraint *pconst;\
+        \
+        if (!sscanf(dev_attr->attr.name, "constraint_%d_", &id)) \
+                return -EINVAL; \
+        if (id >= power_zone->const_id_cnt)     \
+                return -EINVAL; \
+        pconst = &power_zone->constraints[id]; \
+        err = kstrtoull(buf, 10, &value); \
+        if (err) \
+                return -EINVAL; \
+        if (pconst && pconst->ops && pconst->ops->set_##_attr) { \
+                if (!pconst->ops->set_##_attr(power_zone, id, value)) \
+                        return count; \
+        } \
+        \
+        return -ENODATA; \
+}
+
+/* Power zone information callbacks */
+define_power_zone_show(power_uw);
+define_power_zone_show(max_power_range_uw);
+define_power_zone_show(energy_uj);
+define_power_zone_store(energy_uj);
+define_power_zone_show(max_energy_range_uj);
+
+/* Power zone attributes */
+static DEVICE_ATTR_RO(max_power_range_uw);
+static DEVICE_ATTR_RO(power_uw);
+static DEVICE_ATTR_RO(max_energy_range_uj);
+static DEVICE_ATTR_RW(energy_uj);
+
+/* Power zone constraint attributes callbacks */
+define_power_zone_constraint_show(power_limit_uw);
+define_power_zone_constraint_store(power_limit_uw);
+define_power_zone_constraint_show(time_window_us);
+define_power_zone_constraint_store(time_window_us);
+define_power_zone_constraint_show(max_power_uw);
+define_power_zone_constraint_show(min_power_uw);
+define_power_zone_constraint_show(max_time_window_us);
+define_power_zone_constraint_show(min_time_window_us);
+
+/* For one time seeding of constraint device attributes */
+struct powercap_constraint_attr {
+        struct device_attribute power_limit_attr;
+        struct device_attribute time_window_attr;
+        struct device_attribute max_power_attr;
+        struct device_attribute min_power_attr;
+        struct device_attribute max_time_window_attr;
+        struct device_attribute min_time_window_attr;
+        struct device_attribute name_attr;
+};
+
+static struct powercap_constraint_attr
+                                constraint_attrs[MAX_CONSTRAINTS_PER_ZONE];
+
+/* A list of powercap control_types */
+static LIST_HEAD(powercap_cntrl_list);
+/* Mutex to protect list of powercap control_types */
+static DEFINE_MUTEX(powercap_cntrl_list_lock);
+
+#define POWERCAP_CONSTRAINT_NAME_LEN    30 /* Some limit to avoid overflow */
+static ssize_t show_constraint_name(struct device *dev,
+                                struct device_attribute *dev_attr,
+                                char *buf)
+{
+        const char *name;
+        struct powercap_zone *power_zone = to_powercap_zone(dev);
+        int id;
+        ssize_t len = -ENODATA;
+        struct powercap_zone_constraint *pconst;
+
+        if (!sscanf(dev_attr->attr.name, "constraint_%d_", &id))
+                return -EINVAL;
+        if (id >= power_zone->const_id_cnt)
+                return -EINVAL;
+        pconst = &power_zone->constraints[id];
+
+        if (pconst && pconst->ops && pconst->ops->get_name) {
+                name = pconst->ops->get_name(power_zone, id);
+                if (name) {
+                        snprintf(buf, POWERCAP_CONSTRAINT_NAME_LEN,
+                                                                "%s\n", name);
+                        buf[POWERCAP_CONSTRAINT_NAME_LEN] = '\0';
+                        len = strlen(buf);
+                }
+        }
+
+        return len;
+}
+
+static int create_constraint_attribute(int id, const char *name,
+                                int mode,
+                                struct device_attribute *dev_attr,
+                                ssize_t (*show)(struct device *,
+                                        struct device_attribute *, char *),
+                                ssize_t (*store)(struct device *,
+                                        struct device_attribute *,
+                                const char *, size_t)
+                                )
+{
+
+        dev_attr->attr.name = kasprintf(GFP_KERNEL, "constraint_%d_%s",
+                                                                id, name);
+        if (!dev_attr->attr.name)
+                return -ENOMEM;
+        dev_attr->attr.mode = mode;
+        dev_attr->show = show;
+        dev_attr->store = store;
+
+        return 0;
+}
+
+static void free_constraint_attributes(void)
+{
+        int i;
+
+        for (i = 0; i < MAX_CONSTRAINTS_PER_ZONE; ++i) {
+                kfree(constraint_attrs[i].power_limit_attr.attr.name);
+                kfree(constraint_attrs[i].time_window_attr.attr.name);
+                kfree(constraint_attrs[i].name_attr.attr.name);
+                kfree(constraint_attrs[i].max_power_attr.attr.name);
+                kfree(constraint_attrs[i].min_power_attr.attr.name);
+                kfree(constraint_attrs[i].max_time_window_attr.attr.name);
+                kfree(constraint_attrs[i].min_time_window_attr.attr.name);
+        }
+}
+
+static int seed_constraint_attributes(void)
+{
+        int i;
+        int ret;
+
+        for (i = 0; i < MAX_CONSTRAINTS_PER_ZONE; ++i) {
+                ret = create_constraint_attribute(i, "power_limit_uw",
+                                        S_IWUSR | S_IRUGO,
+                                        &constraint_attrs[i].power_limit_attr,
+                                        show_constraint_power_limit_uw,
+                                        store_constraint_power_limit_uw);
+                if (ret)
+                        goto err_alloc;
+                ret = create_constraint_attribute(i, "time_window_us",
+                                        S_IWUSR | S_IRUGO,
+                                        &constraint_attrs[i].time_window_attr,
+                                        show_constraint_time_window_us,
+                                        store_constraint_time_window_us);
+                if (ret)
+                        goto err_alloc;
+                ret = create_constraint_attribute(i, "name", S_IRUGO,
+                                &constraint_attrs[i].name_attr,
+                                show_constraint_name,
+                                NULL);
+                if (ret)
+                        goto err_alloc;
+                ret = create_constraint_attribute(i, "max_power_uw", S_IRUGO,
+                                &constraint_attrs[i].max_power_attr,
+                                show_constraint_max_power_uw,
+                                NULL);
+                if (ret)
+                        goto err_alloc;
+                ret = create_constraint_attribute(i, "min_power_uw", S_IRUGO,
+                                &constraint_attrs[i].min_power_attr,
+                                show_constraint_min_power_uw,
+                                NULL);
+                if (ret)
+                        goto err_alloc;
+                ret = create_constraint_attribute(i, "max_time_window_us",
+                                S_IRUGO,
+                                &constraint_attrs[i].max_time_window_attr,
+                                show_constraint_max_time_window_us,
+                                NULL);
+                if (ret)
+                        goto err_alloc;
+                ret = create_constraint_attribute(i, "min_time_window_us",
+                                S_IRUGO,
+                                &constraint_attrs[i].min_time_window_attr,
+                                show_constraint_min_time_window_us,
+                                NULL);
+                if (ret)
+                        goto err_alloc;
+
+        }
+
+        return 0;
+
+err_alloc:
+        free_constraint_attributes();
+
+        return ret;
+}
+
+static int create_constraints(struct powercap_zone *power_zone,
+                                int nr_constraints,
+                                struct powercap_zone_constraint_ops *const_ops)
+{
+        int i;
+        int ret = 0;
+        int count;
+        struct powercap_zone_constraint *pconst;
+
+        if (!power_zone || !const_ops || !const_ops->get_power_limit_uw ||
+                                        !const_ops->set_power_limit_uw ||
+                                        !const_ops->get_time_window_us ||
+                                        !const_ops->set_time_window_us)
+                return -EINVAL;
+
+        count = power_zone->zone_attr_count;
+        for (i = 0; i < nr_constraints; ++i) {
+                pconst = &power_zone->constraints[i];
+                pconst->ops = const_ops;
+                pconst->id = power_zone->const_id_cnt;
+                power_zone->const_id_cnt++;
+                power_zone->zone_dev_attrs[count++] =
+                                &constraint_attrs[i].power_limit_attr.attr;
+                power_zone->zone_dev_attrs[count++] =
+                                &constraint_attrs[i].time_window_attr.attr;
+                if (pconst->ops->get_name)
+                        power_zone->zone_dev_attrs[count++] =
+                                &constraint_attrs[i].name_attr.attr;
+                if (pconst->ops->get_max_power_uw)
+                        power_zone->zone_dev_attrs[count++] =
+                                &constraint_attrs[i].max_power_attr.attr;
+                if (pconst->ops->get_min_power_uw)
+                        power_zone->zone_dev_attrs[count++] =
+                                &constraint_attrs[i].min_power_attr.attr;
+                if (pconst->ops->get_max_time_window_us)
+                        power_zone->zone_dev_attrs[count++] =
+                                &constraint_attrs[i].max_time_window_attr.attr;
+                if (pconst->ops->get_min_time_window_us)
+                        power_zone->zone_dev_attrs[count++] =
+                                &constraint_attrs[i].min_time_window_attr.attr;
+        }
+        power_zone->zone_attr_count = count;
+
+        return ret;
+}
+
+static bool control_type_valid(void *control_type)
+{
+        struct powercap_control_type *pos = NULL;
+        bool found = false;
+
+        mutex_lock(&powercap_cntrl_list_lock);
+
+        list_for_each_entry(pos, &powercap_cntrl_list, node) {
+                if (pos == control_type) {
+                        found = true;
+                        break;
+                }
+        }
+        mutex_unlock(&powercap_cntrl_list_lock);
+
+        return found;
+}
+
+static ssize_t name_show(struct device *dev,
+                                struct device_attribute *attr,
+                                char *buf)
+{
+        struct powercap_zone *power_zone = to_powercap_zone(dev);
+
+        return sprintf(buf, "%s\n", power_zone->name);
+}
+
+static DEVICE_ATTR_RO(name);
+
+/* Create zone and attributes in sysfs */
+static void create_power_zone_common_attributes(
+                                        struct powercap_zone *power_zone)
+{
+        int count = 0;
+
+        power_zone->zone_dev_attrs[count++] = &dev_attr_name.attr;
+        if (power_zone->ops->get_max_energy_range_uj)
+                power_zone->zone_dev_attrs[count++] =
+                                        &dev_attr_max_energy_range_uj.attr;
+        if (power_zone->ops->get_energy_uj)
+                power_zone->zone_dev_attrs[count++] =
+                                        &dev_attr_energy_uj.attr;
+        if (power_zone->ops->get_power_uw)
+                power_zone->zone_dev_attrs[count++] =
+                                        &dev_attr_power_uw.attr;
+        if (power_zone->ops->get_max_power_range_uw)
+                power_zone->zone_dev_attrs[count++] =
+                                        &dev_attr_max_power_range_uw.attr;
+        power_zone->zone_dev_attrs[count] = NULL;
+        power_zone->zone_attr_count = count;
+}
+
+static void powercap_release(struct device *dev)
+{
+        bool allocated;
+
+        if (dev->parent) {
+                struct powercap_zone *power_zone = to_powercap_zone(dev);
+
+                /* Store flag as the release() may free memory */
+                allocated = power_zone->allocated;
+                /* Remove id from parent idr struct */
+                idr_remove(power_zone->parent_idr, power_zone->id);
+                /* Destroy idrs allocated for this zone */
+                idr_destroy(&power_zone->idr);
+                kfree(power_zone->name);
+                kfree(power_zone->zone_dev_attrs);
+                kfree(power_zone->constraints);
+                if (power_zone->ops->release)
+                        power_zone->ops->release(power_zone);
+                if (allocated)
+                        kfree(power_zone);
+        } else {
+                struct powercap_control_type *control_type =
+                                                to_powercap_control_type(dev);
+
+                /* Store flag as the release() may free memory */
+                allocated = control_type->allocated;
+                idr_destroy(&control_type->idr);
+                mutex_destroy(&control_type->lock);
+                if (control_type->ops && control_type->ops->release)
+                        control_type->ops->release(control_type);
+                if (allocated)
+                        kfree(control_type);
+        }
+}
+
+static ssize_t enabled_show(struct device *dev,
+                                struct device_attribute *attr,
+                                char *buf)
+{
+        bool mode = true;
+
+        /* Default is enabled */
+        if (dev->parent) {
+                struct powercap_zone *power_zone = to_powercap_zone(dev);
+                if (power_zone->ops->get_enable)
+                        if (power_zone->ops->get_enable(power_zone, &mode))
+                                mode = false;
+        } else {
+                struct powercap_control_type *control_type =
+                                                to_powercap_control_type(dev);
+                if (control_type->ops && control_type->ops->get_enable)
+                        if (control_type->ops->get_enable(control_type, &mode))
+                                mode = false;
+        }
+
+        return sprintf(buf, "%d\n", mode);
+}
+
+static ssize_t enabled_store(struct device *dev,
+                                struct device_attribute *attr,
+                                const char *buf,  size_t len)
+{
+        bool mode;
+
+        if (strtobool(buf, &mode))
+                return -EINVAL;
+        if (dev->parent) {
+                struct powercap_zone *power_zone = to_powercap_zone(dev);
+                if (power_zone->ops->set_enable)
+                        if (!power_zone->ops->set_enable(power_zone, mode))
+                                return len;
+        } else {
+                struct powercap_control_type *control_type =
+                                                to_powercap_control_type(dev);
+                if (control_type->ops && control_type->ops->set_enable)
+                        if (!control_type->ops->set_enable(control_type, mode))
+                                return len;
+        }
+
+        return -ENOSYS;
+}
+
+static struct device_attribute powercap_def_attrs[] = {
+                __ATTR(enabled, S_IWUSR | S_IRUGO, enabled_show,
+                                                        enabled_store),
+                __ATTR_NULL
+};
+
+static struct class powercap_class = {
+        .name = "powercap",
+        .dev_release = powercap_release,
+        .dev_attrs = powercap_def_attrs,
+};
+
+struct powercap_zone *powercap_register_zone(
+                                struct powercap_zone *power_zone,
+                                struct powercap_control_type *control_type,
+                                const char *name,
+                                struct powercap_zone *parent,
+                                const struct powercap_zone_ops *ops,
+                                int nr_constraints,
+                                struct powercap_zone_constraint_ops *const_ops)
+{
+        int result;
+        int nr_attrs;
+
+        if (!name || !control_type || !ops ||
+                        nr_constraints > MAX_CONSTRAINTS_PER_ZONE ||
+                        (!ops->get_energy_uj && !ops->get_power_uw) ||
+                        !control_type_valid(control_type))
+                return ERR_PTR(-EINVAL);
+
+        if (power_zone) {
+                if (!ops->release)
+                        return ERR_PTR(-EINVAL);
+                memset(power_zone, 0, sizeof(*power_zone));
+        } else {
+                power_zone = kzalloc(sizeof(*power_zone), GFP_KERNEL);
+                if (!power_zone)
+                        return ERR_PTR(-ENOMEM);
+                power_zone->allocated = true;
+        }
+        power_zone->ops = ops;
+        power_zone->control_type_inst = control_type;
+        if (!parent) {
+                power_zone->dev.parent = &control_type->dev;
+                power_zone->parent_idr = &control_type->idr;
+        } else {
+                power_zone->dev.parent = &parent->dev;
+                power_zone->parent_idr = &parent->idr;
+        }
+        power_zone->dev.class = &powercap_class;
+
+        mutex_lock(&control_type->lock);
+        /* Using idr to get the unique id */
+        result = idr_alloc(power_zone->parent_idr, NULL, 0, 0, GFP_KERNEL);
+        if (result < 0)
+                goto err_idr_alloc;
+
+        power_zone->id = result;
+        idr_init(&power_zone->idr);
+        power_zone->name = kstrdup(name, GFP_KERNEL);
+        if (!power_zone->name)
+                goto err_name_alloc;
+        dev_set_name(&power_zone->dev, "%s:%x",
+                                        dev_name(power_zone->dev.parent),
+                                        power_zone->id);
+        power_zone->constraints = kzalloc(sizeof(*power_zone->constraints) *
+                                         nr_constraints, GFP_KERNEL);
+        if (!power_zone->constraints)
+                goto err_const_alloc;
+
+        nr_attrs = nr_constraints * POWERCAP_CONSTRAINTS_ATTRS +
+                                                POWERCAP_ZONE_MAX_ATTRS + 1;
+        power_zone->zone_dev_attrs = kzalloc(sizeof(void *) *
+                                                nr_attrs, GFP_KERNEL);
+        if (!power_zone->zone_dev_attrs)
+                goto err_attr_alloc;
+        create_power_zone_common_attributes(power_zone);
+        result = create_constraints(power_zone, nr_constraints, const_ops);
+        if (result)
+                goto err_dev_ret;
+
+        power_zone->zone_dev_attrs[power_zone->zone_attr_count] = NULL;
+        power_zone->dev_zone_attr_group.attrs = power_zone->zone_dev_attrs;
+        power_zone->dev_attr_groups[0] = &power_zone->dev_zone_attr_group;
+        power_zone->dev_attr_groups[1] = NULL;
+        power_zone->dev.groups = power_zone->dev_attr_groups;
+        result = device_register(&power_zone->dev);
+        if (result)
+                goto err_dev_ret;
+
+        control_type->nr_zones++;
+        mutex_unlock(&control_type->lock);
+
+        return power_zone;
+
+err_dev_ret:
+        kfree(power_zone->zone_dev_attrs);
+err_attr_alloc:
+        kfree(power_zone->constraints);
+err_const_alloc:
+        kfree(power_zone->name);
+err_name_alloc:
+        idr_remove(power_zone->parent_idr, power_zone->id);
+err_idr_alloc:
+        if (power_zone->allocated)
+                kfree(power_zone);
+        mutex_unlock(&control_type->lock);
+
+        return ERR_PTR(result);
+}
+EXPORT_SYMBOL_GPL(powercap_register_zone);
+
+int powercap_unregister_zone(struct powercap_control_type *control_type,
+                                struct powercap_zone *power_zone)
+{
+        if (!power_zone || !control_type)
+                return -EINVAL;
+
+        mutex_lock(&control_type->lock);
+        control_type->nr_zones--;
+        mutex_unlock(&control_type->lock);
+
+        device_unregister(&power_zone->dev);
+
+        return 0;
+}
+EXPORT_SYMBOL_GPL(powercap_unregister_zone);
+
+struct powercap_control_type *powercap_register_control_type(
+                                struct powercap_control_type *control_type,
+                                const char *name,
+                                const struct powercap_control_type_ops *ops)
+{
+        int result;
+
+        if (!name)
+                return ERR_PTR(-EINVAL);
+        if (control_type) {
+                if (!ops || !ops->release)
+                        return ERR_PTR(-EINVAL);
+                memset(control_type, 0, sizeof(*control_type));
+        } else {
+                control_type = kzalloc(sizeof(*control_type), GFP_KERNEL);
+                if (!control_type)
+                        return ERR_PTR(-ENOMEM);
+                control_type->allocated = true;
+        }
+        mutex_init(&control_type->lock);
+        control_type->ops = ops;
+        INIT_LIST_HEAD(&control_type->node);
+        control_type->dev.class = &powercap_class;
+        dev_set_name(&control_type->dev, name);
+        result = device_register(&control_type->dev);
+        if (result) {
+                if (control_type->allocated)
+                        kfree(control_type);
+                return ERR_PTR(result);
+        }
+        idr_init(&control_type->idr);
+
+        mutex_lock(&powercap_cntrl_list_lock);
+        list_add_tail(&control_type->node, &powercap_cntrl_list);
+        mutex_unlock(&powercap_cntrl_list_lock);
+
+        return control_type;
+}
+EXPORT_SYMBOL_GPL(powercap_register_control_type);
+
+int powercap_unregister_control_type(struct powercap_control_type *control_type)
+{
+        struct powercap_control_type *pos = NULL;
+
+        if (control_type->nr_zones) {
+                dev_err(&control_type->dev, "Zones of this type still not freed\n");
+                return -EINVAL;
+        }
+        mutex_lock(&powercap_cntrl_list_lock);
+        list_for_each_entry(pos, &powercap_cntrl_list, node) {
+                if (pos == control_type) {
+                        list_del(&control_type->node);
+                        mutex_unlock(&powercap_cntrl_list_lock);
+                        device_unregister(&control_type->dev);
+                        return 0;
+                }
+        }
+        mutex_unlock(&powercap_cntrl_list_lock);
+
+        return -ENODEV;
+}
+EXPORT_SYMBOL_GPL(powercap_unregister_control_type);
+
+static int __init powercap_init(void)
+{
+        int result = 0;
+
+        result = seed_constraint_attributes();
+        if (result)
+                return result;
+
+        result = class_register(&powercap_class);
+
+        return result;
+}
+
+device_initcall(powercap_init);
+
+MODULE_DESCRIPTION("PowerCap sysfs Driver");
+MODULE_AUTHOR("Srinivas Pandruvada <srinivas.pandruvada@linux.intel.com>");
+MODULE_LICENSE("GPL v2");