Logo Search packages:      
Sourcecode: linux version File versions  Download package

sysfs.c

/*
 * drivers/base/power/sysfs.c - sysfs entries for device PM
 */

#include <linux/device.h>
#include <linux/string.h>
#include "power.h"


/*
 *    wakeup - Report/change current wakeup option for device
 *
 *    Some devices support "wakeup" events, which are hardware signals
 *    used to activate devices from suspended or low power states.  Such
 *    devices have one of three values for the sysfs power/wakeup file:
 *
 *     + "enabled\n" to issue the events;
 *     + "disabled\n" not to do so; or
 *     + "\n" for temporary or permanent inability to issue wakeup.
 *
 *    (For example, unconfigured USB devices can't issue wakeups.)
 *
 *    Familiar examples of devices that can issue wakeup events include
 *    keyboards and mice (both PS2 and USB styles), power buttons, modems,
 *    "Wake-On-LAN" Ethernet links, GPIO lines, and more.  Some events
 *    will wake the entire system from a suspend state; others may just
 *    wake up the device (if the system as a whole is already active).
 *    Some wakeup events use normal IRQ lines; other use special out
 *    of band signaling.
 *
 *    It is the responsibility of device drivers to enable (or disable)
 *    wakeup signaling as part of changing device power states, respecting
 *    the policy choices provided through the driver model.
 *
 *    Devices may not be able to generate wakeup events from all power
 *    states.  Also, the events may be ignored in some configurations;
 *    for example, they might need help from other devices that aren't
 *    active, or which may have wakeup disabled.  Some drivers rely on
 *    wakeup events internally (unless they are disabled), keeping
 *    their hardware in low power modes whenever they're unused.  This
 *    saves runtime power, without requiring system-wide sleep states.
 */

static const char enabled[] = "enabled";
static const char disabled[] = "disabled";

static ssize_t
wake_show(struct device * dev, struct device_attribute *attr, char * buf)
{
      return sprintf(buf, "%s\n", device_can_wakeup(dev)
            ? (device_may_wakeup(dev) ? enabled : disabled)
            : "");
}

static ssize_t
wake_store(struct device * dev, struct device_attribute *attr,
      const char * buf, size_t n)
{
      char *cp;
      int len = n;

      if (!device_can_wakeup(dev))
            return -EINVAL;

      cp = memchr(buf, '\n', n);
      if (cp)
            len = cp - buf;
      if (len == sizeof enabled - 1
                  && strncmp(buf, enabled, sizeof enabled - 1) == 0)
            device_set_wakeup_enable(dev, 1);
      else if (len == sizeof disabled - 1
                  && strncmp(buf, disabled, sizeof disabled - 1) == 0)
            device_set_wakeup_enable(dev, 0);
      else
            return -EINVAL;
      return n;
}

static DEVICE_ATTR(wakeup, 0644, wake_show, wake_store);


static struct attribute * power_attrs[] = {
      &dev_attr_wakeup.attr,
      NULL,
};
static struct attribute_group pm_attr_group = {
      .name = "power",
      .attrs      = power_attrs,
};

int dpm_sysfs_add(struct device * dev)
{
      return sysfs_create_group(&dev->kobj, &pm_attr_group);
}

void dpm_sysfs_remove(struct device * dev)
{
      sysfs_remove_group(&dev->kobj, &pm_attr_group);
}

Generated by  Doxygen 1.6.0   Back to index