drivers/devfreq/governor_userspace.c

   1 /*
   2  *  linux/drivers/devfreq/governor_userspace.c
   3  *
   4  *  Copyright (C) 2011 Samsung Electronics
   5  *      MyungJoo Ham <myungjoo.ham@samsung.com>
   6  *
   7  * This program is free software; you can redistribute it and/or modify
   8  * it under the terms of the GNU General Public License version 2 as
   9  * published by the Free Software Foundation.
  10  */
  11
  12 #include <linux/slab.h>
  13 #include <linux/device.h>
  14 #include <linux/devfreq.h>
  15 #include <linux/pm.h>
  16 #include <linux/mutex.h>
  17 #include <linux/module.h>
  18 #include "governor.h"
  19
  20 struct userspace_data {
  21         unsigned long user_frequency;
  22         bool valid;
  23 };
  24
  25 static int devfreq_userspace_func(struct devfreq *df, unsigned long *freq)
  26 {
  27         struct userspace_data *data = df->data;
  28
  29         if (data->valid)
  30                 *freq = data->user_frequency;
  31         else
  32                 *freq = df->previous_freq; /* No user freq specified yet */
  33
  34         return 0;
  35 }
  36
  37 static ssize_t store_freq(struct device *dev, struct device_attribute *attr,
  38                           const char *buf, size_t count)
  39 {
  40         struct devfreq *devfreq = to_devfreq(dev);
  41         struct userspace_data *data;
  42         unsigned long wanted;
  43         int err = 0;
  44
  45         mutex_lock(&devfreq->lock);
  46         data = devfreq->data;
  47
  48         sscanf(buf, "%lu", &wanted);
  49         data->user_frequency = wanted;
  50         data->valid = true;
  51         err = update_devfreq(devfreq);
  52         if (err == 0)
  53                 err = count;
  54         mutex_unlock(&devfreq->lock);
  55         return err;
  56 }
  57
  58 static ssize_t show_freq(struct device *dev, struct device_attribute *attr,
  59                          char *buf)
  60 {
  61         struct devfreq *devfreq = to_devfreq(dev);
  62         struct userspace_data *data;
  63         int err = 0;
  64
  65         mutex_lock(&devfreq->lock);
  66         data = devfreq->data;
  67
  68         if (data->valid)
  69                 err = sprintf(buf, "%lu\n", data->user_frequency);
  70         else
  71                 err = sprintf(buf, "undefined\n");
  72         mutex_unlock(&devfreq->lock);
  73         return err;
  74 }
  75
  76 static DEVICE_ATTR(set_freq, 0644, show_freq, store_freq);
  77 static struct attribute *dev_entries[] = {
  78         &dev_attr_set_freq.attr,
  79         NULL,
  80 };
  81 static const struct attribute_group dev_attr_group = {
  82         .name   = DEVFREQ_GOV_USERSPACE,
  83         .attrs  = dev_entries,
  84 };
  85
  86 static int userspace_init(struct devfreq *devfreq)
  87 {
  88         int err = 0;
  89         struct userspace_data *data = kzalloc(sizeof(struct userspace_data),
  90                                               GFP_KERNEL);
  91
  92         if (!data) {
  93                 err = -ENOMEM;
  94                 goto out;
  95         }
  96         data->valid = false;
  97         devfreq->data = data;
  98
  99         err = sysfs_create_group(&devfreq->dev.kobj, &dev_attr_group);
 100 out:
 101         return err;
 102 }
 103
 104 static void userspace_exit(struct devfreq *devfreq)
 105 {
 106         /*
 107          * Remove the sysfs entry, unless this is being called after
 108          * device_del(), which should have done this already via kobject_del().
 109          */
 110         if (devfreq->dev.kobj.sd)
 111                 sysfs_remove_group(&devfreq->dev.kobj, &dev_attr_group);
 112
 113         kfree(devfreq->data);
 114         devfreq->data = NULL;
 115 }
 116
 117 static int devfreq_userspace_handler(struct devfreq *devfreq,
 118                         unsigned int event, void *data)
 119 {
 120         int ret = 0;
 121
 122         switch (event) {
 123         case DEVFREQ_GOV_START:
 124                 ret = userspace_init(devfreq);
 125                 break;
 126         case DEVFREQ_GOV_STOP:
 127                 userspace_exit(devfreq);
 128                 break;
 129         default:
 130                 break;
 131         }
 132
 133         return ret;
 134 }
 135
 136 static struct devfreq_governor devfreq_userspace = {
 137         .name = "userspace",
 138         .get_target_freq = devfreq_userspace_func,
 139         .event_handler = devfreq_userspace_handler,
 140 };
 141
 142 static int __init devfreq_userspace_init(void)
 143 {
 144         return devfreq_add_governor(&devfreq_userspace);
 145 }
 146 subsys_initcall(devfreq_userspace_init);
 147
 148 static void __exit devfreq_userspace_exit(void)
 149 {
 150         int ret;
 151
 152         ret = devfreq_remove_governor(&devfreq_userspace);
 153         if (ret)
 154                 pr_err("%s: failed remove governor %d\n", __func__, ret);
 155
 156         return;
 157 }
 158 module_exit(devfreq_userspace_exit);
 159 MODULE_LICENSE("GPL");