LXR linux/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
  43static const char enabled[] = "enabled";
  44static const char disabled[] = "disabled";
  45
  46static ssize_t
  47wake_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
  54static ssize_t
  55wake_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
  78static DEVICE_ATTR(wakeup, 0644, wake_show, wake_store);
  79
  80
  81static struct attribute * power_attrs[] = {
  82        &dev_attr_wakeup.attr,
  83        NULL,
  84};
  85static struct attribute_group pm_attr_group = {
  86        .name   = "power",
  87        .attrs  = power_attrs,
  88};
  89
  90int dpm_sysfs_add(struct device * dev)
  91{
  92        return sysfs_create_group(&dev->kobj, &pm_attr_group);
  93}
  94
  95void dpm_sysfs_remove(struct device * dev)
  96{
  97        sysfs_remove_group(&dev->kobj, &pm_attr_group);
  98}
  99