drivers/base/power/sysfs.c

   1 /*
   2  * drivers/base/power/sysfs.c - sysfs entries for device PM
   3  */
   4
   5 #include <linux/device.h>
   6 #include "power.h"
   7
   8
   9 /**
  10  *      state - Control current power state of device
  11  *
  12  *      show() returns the current power state of the device. '0' indicates
  13  *      the device is on. Other values (1-3) indicate the device is in a low
  14  *      power state.
  15  *
  16  *      store() sets the current power state, which is an integer value
  17  *      between 0-3. If the device is on ('0'), and the value written is
  18  *      greater than 0, then the device is placed directly into the low-power
  19  *      state (via its driver's ->suspend() method).
  20  *      If the device is currently in a low-power state, and the value is 0,
  21  *      the device is powered back on (via the ->resume() method).
  22  *      If the device is in a low-power state, and a different low-power state
  23  *      is requested, the device is first resumed, then suspended into the new
  24  *      low-power state.
  25  */
  26
  27 static ssize_t state_show(struct device * dev, char * buf)
  28 {
  29         return sprintf(buf, "%u\n", dev->power.power_state);
  30 }
  31
  32 static ssize_t state_store(struct device * dev, const char * buf, size_t n)
  33 {
  34         u32 state;
  35         char * rest;
  36         int error = 0;
  37
  38         state = simple_strtoul(buf, &rest, 10);
  39         if (*rest)
  40                 return -EINVAL;
  41         if (state)
  42                 error = dpm_runtime_suspend(dev, state);
  43         else
  44                 dpm_runtime_resume(dev);
  45         return error ? error : n;
  46 }
  47
  48 static DEVICE_ATTR(state, 0644, state_show, state_store);
  49
  50
  51 static struct attribute * power_attrs[] = {
  52         &dev_attr_state.attr,
  53         NULL,
  54 };
  55 static struct attribute_group pm_attr_group = {
  56         .name   = "power",
  57         .attrs  = power_attrs,
  58 };
  59
  60 int dpm_sysfs_add(struct device * dev)
  61 {
  62         return sysfs_create_group(&dev->kobj, &pm_attr_group);
  63 }
  64
  65 void dpm_sysfs_remove(struct device * dev)
  66 {
  67         sysfs_remove_group(&dev->kobj, &pm_attr_group);
  68 }