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  *      wakeup - Report/change current wakeup option for device
  12  *
  13  *      Some devices support "wakeup" events, which are hardware signals
  14  *      used to activate devices from suspended or low power states.  Such
  15  *      devices have one of three values for the sysfs power/wakeup file:
  16  *
  17  *       + "enabled\n" to issue the events;
  18  *       + "disabled\n" not to do so; or
  19  *       + "\n" for temporary or permanent inability to issue wakeup.
  20  *
  21  *      (For example, unconfigured USB devices can't issue wakeups.)
  22  *
  23  *      Familiar examples of devices that can issue wakeup events include
  24  *      keyboards and mice (both PS2 and USB styles), power buttons, modems,
  25  *      "Wake-On-LAN" Ethernet links, GPIO lines, and more.  Some events
  26  *      will wake the entire system from a suspend state; others may just
  27  *      wake up the device (if the system as a whole is already active).
  28  *      Some wakeup events use normal IRQ lines; other use special out
  29  *      of band signaling.
  30  *
  31  *      It is the responsibility of device drivers to enable (or disable)
  32  *      wakeup signaling as part of changing device power states, respecting
  33  *      the policy choices provided through the driver model.
  34  *
  35  *      Devices may not be able to generate wakeup events from all power
  36  *      states.  Also, the events may be ignored in some configurations;
  37  *      for example, they might need help from other devices that aren't
  38  *      active, or which may have wakeup disabled.  Some drivers rely on
  39  *      wakeup events internally (unless they are disabled), keeping
  40  *      their hardware in low power modes whenever they're unused.  This
  41  *      saves runtime power, without requiring system-wide sleep states.
  42  */
  43
  44 static const char enabled[] = "enabled";
  45 static const char disabled[] = "disabled";
  46
  47 static ssize_t
  48 wake_show(struct device * dev, struct device_attribute *attr, char * buf)
  49 {
  50         return sprintf(buf, "%s\n", device_can_wakeup(dev)
  51                 ? (device_may_wakeup(dev) ? enabled : disabled)
  52                 : "");
  53 }
  54
  55 static ssize_t
  56 wake_store(struct device * dev, struct device_attribute *attr,
  57         const char * buf, size_t n)
  58 {
  59         char *cp;
  60         int len = n;
  61
  62         if (!device_can_wakeup(dev))
  63                 return -EINVAL;
  64
  65         cp = memchr(buf, '\n', n);
  66         if (cp)
  67                 len = cp - buf;
  68         if (len == sizeof enabled - 1
  69                         && strncmp(buf, enabled, sizeof enabled - 1) == 0)
  70                 device_set_wakeup_enable(dev, 1);
  71         else if (len == sizeof disabled - 1
  72                         && strncmp(buf, disabled, sizeof disabled - 1) == 0)
  73                 device_set_wakeup_enable(dev, 0);
  74         else
  75                 return -EINVAL;
  76         return n;
  77 }
  78
  79 static DEVICE_ATTR(wakeup, 0644, wake_show, wake_store);
  80
  81
  82 static struct attribute * power_attrs[] = {
  83         &dev_attr_wakeup.attr,
  84         NULL,
  85 };
  86 static struct attribute_group pm_attr_group = {
  87         .name   = "power",
  88         .attrs  = power_attrs,
  89 };
  90
  91 int dpm_sysfs_add(struct device * dev)
  92 {
  93         return sysfs_create_group(&dev->kobj, &pm_attr_group);
  94 }
  95
  96 void dpm_sysfs_remove(struct device * dev)
  97 {
  98         sysfs_remove_group(&dev->kobj, &pm_attr_group);
  99 }