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 <linux/string.h>
   7 #include "power.h"
   8
   9
  10 /**
  11  *      state - Control current power state of device
  12  *
  13  *      show() returns the current power state of the device. '0' indicates
  14  *      the device is on. Other values (1-3) indicate the device is in a low
  15  *      power state.
  16  *
  17  *      store() sets the current power state, which is an integer value
  18  *      between 0-3. If the device is on ('0'), and the value written is
  19  *      greater than 0, then the device is placed directly into the low-power
  20  *      state (via its driver's ->suspend() method).
  21  *      If the device is currently in a low-power state, and the value is 0,
  22  *      the device is powered back on (via the ->resume() method).
  23  *      If the device is in a low-power state, and a different low-power state
  24  *      is requested, the device is first resumed, then suspended into the new
  25  *      low-power state.
  26  */
  27
  28 static ssize_t state_show(struct device * dev, struct device_attribute *attr, char * buf)
  29 {
  30         return sprintf(buf, "%u\n", dev->power.power_state.event);
  31 }
  32
  33 static ssize_t state_store(struct device * dev, struct device_attribute *attr, const char * buf, size_t n)
  34 {
  35         pm_message_t state;
  36         char * rest;
  37         int error = 0;
  38
  39         state.event = simple_strtoul(buf, &rest, 10);
  40         if (*rest)
  41                 return -EINVAL;
  42         if (state.event)
  43                 error = dpm_runtime_suspend(dev, state);
  44         else
  45                 dpm_runtime_resume(dev);
  46         return error ? error : n;
  47 }
  48
  49 static DEVICE_ATTR(state, 0644, state_show, state_store);
  50
  51
  52 /*
  53  *      wakeup - Report/change current wakeup option for device
  54  *
  55  *      Some devices support "wakeup" events, which are hardware signals
  56  *      used to activate devices from suspended or low power states.  Such
  57  *      devices have one of three values for the sysfs power/wakeup file:
  58  *
  59  *       + "enabled\n" to issue the events;
  60  *       + "disabled\n" not to do so; or
  61  *       + "\n" for temporary or permanent inability to issue wakeup.
  62  *
  63  *      (For example, unconfigured USB devices can't issue wakeups.)
  64  *
  65  *      Familiar examples of devices that can issue wakeup events include
  66  *      keyboards and mice (both PS2 and USB styles), power buttons, modems,
  67  *      "Wake-On-LAN" Ethernet links, GPIO lines, and more.  Some events
  68  *      will wake the entire system from a suspend state; others may just
  69  *      wake up the device (if the system as a whole is already active).
  70  *      Some wakeup events use normal IRQ lines; other use special out
  71  *      of band signaling.
  72  *
  73  *      It is the responsibility of device drivers to enable (or disable)
  74  *      wakeup signaling as part of changing device power states, respecting
  75  *      the policy choices provided through the driver model.
  76  *
  77  *      Devices may not be able to generate wakeup events from all power
  78  *      states.  Also, the events may be ignored in some configurations;
  79  *      for example, they might need help from other devices that aren't
  80  *      active, or which may have wakeup disabled.  Some drivers rely on
  81  *      wakeup events internally (unless they are disabled), keeping
  82  *      their hardware in low power modes whenever they're unused.  This
  83  *      saves runtime power, without requiring system-wide sleep states.
  84  */
  85
  86 static const char enabled[] = "enabled";
  87 static const char disabled[] = "disabled";
  88
  89 static ssize_t
  90 wake_show(struct device * dev, struct device_attribute *attr, char * buf)
  91 {
  92         return sprintf(buf, "%s\n", device_can_wakeup(dev)
  93                 ? (device_may_wakeup(dev) ? enabled : disabled)
  94                 : "");
  95 }
  96
  97 static ssize_t
  98 wake_store(struct device * dev, struct device_attribute *attr,
  99         const char * buf, size_t n)
 100 {
 101         char *cp;
 102         int len = n;
 103
 104         if (!device_can_wakeup(dev))
 105                 return -EINVAL;
 106
 107         cp = memchr(buf, '\n', n);
 108         if (cp)
 109                 len = cp - buf;
 110         if (len == sizeof enabled - 1
 111                         && strncmp(buf, enabled, sizeof enabled - 1) == 0)
 112                 device_set_wakeup_enable(dev, 1);
 113         else if (len == sizeof disabled - 1
 114                         && strncmp(buf, disabled, sizeof disabled - 1) == 0)
 115                 device_set_wakeup_enable(dev, 0);
 116         else
 117                 return -EINVAL;
 118         return n;
 119 }
 120
 121 static DEVICE_ATTR(wakeup, 0644, wake_show, wake_store);
 122
 123
 124 static struct attribute * power_attrs[] = {
 125         &dev_attr_state.attr,
 126         &dev_attr_wakeup.attr,
 127         NULL,
 128 };
 129 static struct attribute_group pm_attr_group = {
 130         .name   = "power",
 131         .attrs  = power_attrs,
 132 };
 133
 134 int dpm_sysfs_add(struct device * dev)
 135 {
 136         return sysfs_create_group(&dev->kobj, &pm_attr_group);
 137 }
 138
 139 void dpm_sysfs_remove(struct device * dev)
 140 {
 141         sysfs_remove_group(&dev->kobj, &pm_attr_group);
 142 }