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 <linux/pm_runtime.h>
   8 #include "power.h"
   9
  10 /*
  11  *      control - Report/change current runtime PM setting of the device
  12  *
  13  *      Runtime power management of a device can be blocked with the help of
  14  *      this attribute.  All devices have one of the following two values for
  15  *      the power/control file:
  16  *
  17  *       + "auto\n" to allow the device to be power managed at run time;
  18  *       + "on\n" to prevent the device from being power managed at run time;
  19  *
  20  *      The default for all devices is "auto", which means that devices may be
  21  *      subject to automatic power management, depending on their drivers.
  22  *      Changing this attribute to "on" prevents the driver from power managing
  23  *      the device at run time.  Doing that while the device is suspended causes
  24  *      it to be woken up.
  25  *
  26  *      wakeup - Report/change current wakeup option for device
  27  *
  28  *      Some devices support "wakeup" events, which are hardware signals
  29  *      used to activate devices from suspended or low power states.  Such
  30  *      devices have one of three values for the sysfs power/wakeup file:
  31  *
  32  *       + "enabled\n" to issue the events;
  33  *       + "disabled\n" not to do so; or
  34  *       + "\n" for temporary or permanent inability to issue wakeup.
  35  *
  36  *      (For example, unconfigured USB devices can't issue wakeups.)
  37  *
  38  *      Familiar examples of devices that can issue wakeup events include
  39  *      keyboards and mice (both PS2 and USB styles), power buttons, modems,
  40  *      "Wake-On-LAN" Ethernet links, GPIO lines, and more.  Some events
  41  *      will wake the entire system from a suspend state; others may just
  42  *      wake up the device (if the system as a whole is already active).
  43  *      Some wakeup events use normal IRQ lines; other use special out
  44  *      of band signaling.
  45  *
  46  *      It is the responsibility of device drivers to enable (or disable)
  47  *      wakeup signaling as part of changing device power states, respecting
  48  *      the policy choices provided through the driver model.
  49  *
  50  *      Devices may not be able to generate wakeup events from all power
  51  *      states.  Also, the events may be ignored in some configurations;
  52  *      for example, they might need help from other devices that aren't
  53  *      active, or which may have wakeup disabled.  Some drivers rely on
  54  *      wakeup events internally (unless they are disabled), keeping
  55  *      their hardware in low power modes whenever they're unused.  This
  56  *      saves runtime power, without requiring system-wide sleep states.
  57  *
  58  *      async - Report/change current async suspend setting for the device
  59  *
  60  *      Asynchronous suspend and resume of the device during system-wide power
  61  *      state transitions can be enabled by writing "enabled" to this file.
  62  *      Analogously, if "disabled" is written to this file, the device will be
  63  *      suspended and resumed synchronously.
  64  *
  65  *      All devices have one of the following two values for power/async:
  66  *
  67  *       + "enabled\n" to permit the asynchronous suspend/resume of the device;
  68  *       + "disabled\n" to forbid it;
  69  *
  70  *      NOTE: It generally is unsafe to permit the asynchronous suspend/resume
  71  *      of a device unless it is certain that all of the PM dependencies of the
  72  *      device are known to the PM core.  However, for some devices this
  73  *      attribute is set to "enabled" by bus type code or device drivers and in
  74  *      that cases it should be safe to leave the default value.
  75  */
  76
  77 static const char enabled[] = "enabled";
  78 static const char disabled[] = "disabled";
  79
  80 #ifdef CONFIG_PM_RUNTIME
  81 static const char ctrl_auto[] = "auto";
  82 static const char ctrl_on[] = "on";
  83
  84 static ssize_t control_show(struct device *dev, struct device_attribute *attr,
  85                             char *buf)
  86 {
  87         return sprintf(buf, "%s\n",
  88                                 dev->power.runtime_auto ? ctrl_auto : ctrl_on);
  89 }
  90
  91 static ssize_t control_store(struct device * dev, struct device_attribute *attr,
  92                              const char * buf, size_t n)
  93 {
  94         char *cp;
  95         int len = n;
  96
  97         cp = memchr(buf, '\n', n);
  98         if (cp)
  99                 len = cp - buf;
 100         if (len == sizeof ctrl_auto - 1 && strncmp(buf, ctrl_auto, len) == 0)
 101                 pm_runtime_allow(dev);
 102         else if (len == sizeof ctrl_on - 1 && strncmp(buf, ctrl_on, len) == 0)
 103                 pm_runtime_forbid(dev);
 104         else
 105                 return -EINVAL;
 106         return n;
 107 }
 108
 109 static DEVICE_ATTR(control, 0644, control_show, control_store);
 110 #endif
 111
 112 static ssize_t
 113 wake_show(struct device * dev, struct device_attribute *attr, char * buf)
 114 {
 115         return sprintf(buf, "%s\n", device_can_wakeup(dev)
 116                 ? (device_may_wakeup(dev) ? enabled : disabled)
 117                 : "");
 118 }
 119
 120 static ssize_t
 121 wake_store(struct device * dev, struct device_attribute *attr,
 122         const char * buf, size_t n)
 123 {
 124         char *cp;
 125         int len = n;
 126
 127         if (!device_can_wakeup(dev))
 128                 return -EINVAL;
 129
 130         cp = memchr(buf, '\n', n);
 131         if (cp)
 132                 len = cp - buf;
 133         if (len == sizeof enabled - 1
 134                         && strncmp(buf, enabled, sizeof enabled - 1) == 0)
 135                 device_set_wakeup_enable(dev, 1);
 136         else if (len == sizeof disabled - 1
 137                         && strncmp(buf, disabled, sizeof disabled - 1) == 0)
 138                 device_set_wakeup_enable(dev, 0);
 139         else
 140                 return -EINVAL;
 141         return n;
 142 }
 143
 144 static DEVICE_ATTR(wakeup, 0644, wake_show, wake_store);
 145
 146 #ifdef CONFIG_PM_SLEEP_ADVANCED_DEBUG
 147 static ssize_t async_show(struct device *dev, struct device_attribute *attr,
 148                           char *buf)
 149 {
 150         return sprintf(buf, "%s\n",
 151                         device_async_suspend_enabled(dev) ? enabled : disabled);
 152 }
 153
 154 static ssize_t async_store(struct device *dev, struct device_attribute *attr,
 155                            const char *buf, size_t n)
 156 {
 157         char *cp;
 158         int len = n;
 159
 160         cp = memchr(buf, '\n', n);
 161         if (cp)
 162                 len = cp - buf;
 163         if (len == sizeof enabled - 1 && strncmp(buf, enabled, len) == 0)
 164                 device_enable_async_suspend(dev);
 165         else if (len == sizeof disabled - 1 && strncmp(buf, disabled, len) == 0)
 166                 device_disable_async_suspend(dev);
 167         else
 168                 return -EINVAL;
 169         return n;
 170 }
 171
 172 static DEVICE_ATTR(async, 0644, async_show, async_store);
 173 #endif /* CONFIG_PM_SLEEP_ADVANCED_DEBUG */
 174
 175 static struct attribute * power_attrs[] = {
 176 #ifdef CONFIG_PM_RUNTIME
 177         &dev_attr_control.attr,
 178 #endif
 179         &dev_attr_wakeup.attr,
 180 #ifdef CONFIG_PM_SLEEP_ADVANCED_DEBUG
 181         &dev_attr_async.attr,
 182 #endif
 183         NULL,
 184 };
 185 static struct attribute_group pm_attr_group = {
 186         .name   = "power",
 187         .attrs  = power_attrs,
 188 };
 189
 190 int dpm_sysfs_add(struct device * dev)
 191 {
 192         return sysfs_create_group(&dev->kobj, &pm_attr_group);
 193 }
 194
 195 void dpm_sysfs_remove(struct device * dev)
 196 {
 197         sysfs_remove_group(&dev->kobj, &pm_attr_group);
 198 }