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  *      wakeup - Report/change current wakeup option for device
  11  *
  12  *      Some devices support "wakeup" events, which are hardware signals
  13  *      used to activate devices from suspended or low power states.  Such
  14  *      devices have one of three values for the sysfs power/wakeup file:
  15  *
  16  *       + "enabled\n" to issue the events;
  17  *       + "disabled\n" not to do so; or
  18  *       + "\n" for temporary or permanent inability to issue wakeup.
  19  *
  20  *      (For example, unconfigured USB devices can't issue wakeups.)
  21  *
  22  *      Familiar examples of devices that can issue wakeup events include
  23  *      keyboards and mice (both PS2 and USB styles), power buttons, modems,
  24  *      "Wake-On-LAN" Ethernet links, GPIO lines, and more.  Some events
  25  *      will wake the entire system from a suspend state; others may just
  26  *      wake up the device (if the system as a whole is already active).
  27  *      Some wakeup events use normal IRQ lines; other use special out
  28  *      of band signaling.
  29  *
  30  *      It is the responsibility of device drivers to enable (or disable)
  31  *      wakeup signaling as part of changing device power states, respecting
  32  *      the policy choices provided through the driver model.
  33  *
  34  *      Devices may not be able to generate wakeup events from all power
  35  *      states.  Also, the events may be ignored in some configurations;
  36  *      for example, they might need help from other devices that aren't
  37  *      active, or which may have wakeup disabled.  Some drivers rely on
  38  *      wakeup events internally (unless they are disabled), keeping
  39  *      their hardware in low power modes whenever they're unused.  This
  40  *      saves runtime power, without requiring system-wide sleep states.
  41  */
  42
  43 static const char enabled[] = "enabled";
  44 static const char disabled[] = "disabled";
  45
  46 static ssize_t
  47 wake_show(struct device * dev, struct device_attribute *attr, char * buf)
  48 {
  49         return sprintf(buf, "%s\n", device_can_wakeup(dev)
  50                 ? (device_may_wakeup(dev) ? enabled : disabled)
  51                 : "");
  52 }
  53
  54 static ssize_t
  55 wake_store(struct device * dev, struct device_attribute *attr,
  56         const char * buf, size_t n)
  57 {
  58         char *cp;
  59         int len = n;
  60
  61         if (!device_can_wakeup(dev))
  62                 return -EINVAL;
  63
  64         cp = memchr(buf, '\n', n);
  65         if (cp)
  66                 len = cp - buf;
  67         if (len == sizeof enabled - 1
  68                         && strncmp(buf, enabled, sizeof enabled - 1) == 0)
  69                 device_set_wakeup_enable(dev, 1);
  70         else if (len == sizeof disabled - 1
  71                         && strncmp(buf, disabled, sizeof disabled - 1) == 0)
  72                 device_set_wakeup_enable(dev, 0);
  73         else
  74                 return -EINVAL;
  75         return n;
  76 }
  77
  78 static DEVICE_ATTR(wakeup, 0644, wake_show, wake_store);
  79
  80
  81 static struct attribute * power_attrs[] = {
  82         &dev_attr_wakeup.attr,
  83         NULL,
  84 };
  85 static struct attribute_group pm_attr_group = {
  86         .name   = "power",
  87         .attrs  = power_attrs,
  88 };
  89
  90 int dpm_sysfs_add(struct device * dev)
  91 {
  92         return sysfs_create_group(&dev->kobj, &pm_attr_group);
  93 }
  94
  95 void dpm_sysfs_remove(struct device * dev)
  96 {
  97         sysfs_remove_group(&dev->kobj, &pm_attr_group);
  98 }