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marcus.erl |
/*
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* drivers/base/power/sysfs.c - sysfs entries for device PM
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*/
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#include <linux/device.h>
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#include <linux/string.h>
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#include "power.h"
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/*
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* wakeup - Report/change current wakeup option for device
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*
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* Some devices support "wakeup" events, which are hardware signals
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* used to activate devices from suspended or low power states. Such
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* devices have one of three values for the sysfs power/wakeup file:
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*
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* + "enabled\n" to issue the events;
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* + "disabled\n" not to do so; or
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* + "\n" for temporary or permanent inability to issue wakeup.
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*
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* (For example, unconfigured USB devices can't issue wakeups.)
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*
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* Familiar examples of devices that can issue wakeup events include
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* keyboards and mice (both PS2 and USB styles), power buttons, modems,
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* "Wake-On-LAN" Ethernet links, GPIO lines, and more. Some events
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* will wake the entire system from a suspend state; others may just
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* wake up the device (if the system as a whole is already active).
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* Some wakeup events use normal IRQ lines; other use special out
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* of band signaling.
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*
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* It is the responsibility of device drivers to enable (or disable)
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* wakeup signaling as part of changing device power states, respecting
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* the policy choices provided through the driver model.
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*
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* Devices may not be able to generate wakeup events from all power
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* states. Also, the events may be ignored in some configurations;
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* for example, they might need help from other devices that aren't
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* active, or which may have wakeup disabled. Some drivers rely on
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* wakeup events internally (unless they are disabled), keeping
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* their hardware in low power modes whenever they're unused. This
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* saves runtime power, without requiring system-wide sleep states.
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*/
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static const char enabled[] = "enabled";
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static const char disabled[] = "disabled";
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static ssize_t
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wake_show(struct device * dev, struct device_attribute *attr, char * buf)
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{
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return sprintf(buf, "%s\n", device_can_wakeup(dev)
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? (device_may_wakeup(dev) ? enabled : disabled)
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: "");
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}
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static ssize_t
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wake_store(struct device * dev, struct device_attribute *attr,
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const char * buf, size_t n)
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{
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char *cp;
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int len = n;
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if (!device_can_wakeup(dev))
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return -EINVAL;
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cp = memchr(buf, '\n', n);
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if (cp)
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len = cp - buf;
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if (len == sizeof enabled - 1
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&& strncmp(buf, enabled, sizeof enabled - 1) == 0)
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device_set_wakeup_enable(dev, 1);
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else if (len == sizeof disabled - 1
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&& strncmp(buf, disabled, sizeof disabled - 1) == 0)
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device_set_wakeup_enable(dev, 0);
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else
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return -EINVAL;
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return n;
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}
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static DEVICE_ATTR(wakeup, 0644, wake_show, wake_store);
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static struct attribute * power_attrs[] = {
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&dev_attr_wakeup.attr,
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NULL,
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};
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static struct attribute_group pm_attr_group = {
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.name = "power",
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.attrs = power_attrs,
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};
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int dpm_sysfs_add(struct device * dev)
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{
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return sysfs_create_group(&dev->kobj, &pm_attr_group);
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}
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void dpm_sysfs_remove(struct device * dev)
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{
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sysfs_remove_group(&dev->kobj, &pm_attr_group);
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}
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