1What: /sys/devices/.../power/ 2Date: January 2009 3Contact: Rafael J. Wysocki <rjw@sisk.pl> 4Description: 5 The /sys/devices/.../power directory contains attributes 6 allowing the user space to check and modify some power 7 management related properties of given device. 8 9What: /sys/devices/.../power/wakeup 10Date: January 2009 11Contact: Rafael J. Wysocki <rjw@sisk.pl> 12Description: 13 The /sys/devices/.../power/wakeup attribute allows the user 14 space to check if the device is enabled to wake up the system 15 from sleep states, such as the memory sleep state (suspend to 16 RAM) and hibernation (suspend to disk), and to enable or disable 17 it to do that as desired. 18 19 Some devices support "wakeup" events, which are hardware signals 20 used to activate the system from a sleep state. Such devices 21 have one of the following two values for the sysfs power/wakeup 22 file: 23 24 + "enabled\n" to issue the events; 25 + "disabled\n" not to do so; 26 27 In that cases the user space can change the setting represented 28 by the contents of this file by writing either "enabled", or 29 "disabled" to it. 30 31 For the devices that are not capable of generating system wakeup 32 events this file contains "\n". In that cases the user space 33 cannot modify the contents of this file and the device cannot be 34 enabled to wake up the system. 35 36What: /sys/devices/.../power/control 37Date: January 2009 38Contact: Rafael J. Wysocki <rjw@sisk.pl> 39Description: 40 The /sys/devices/.../power/control attribute allows the user 41 space to control the run-time power management of the device. 42 43 All devices have one of the following two values for the 44 power/control file: 45 46 + "auto\n" to allow the device to be power managed at run time; 47 + "on\n" to prevent the device from being power managed; 48 49 The default for all devices is "auto", which means that they may 50 be subject to automatic power management, depending on their 51 drivers. Changing this attribute to "on" prevents the driver 52 from power managing the device at run time. Doing that while 53 the device is suspended causes it to be woken up. 54 55What: /sys/devices/.../power/async 56Date: January 2009 57Contact: Rafael J. Wysocki <rjw@sisk.pl> 58Description: 59 The /sys/devices/.../async attribute allows the user space to 60 enable or diasble the device's suspend and resume callbacks to 61 be executed asynchronously (ie. in separate threads, in parallel 62 with the main suspend/resume thread) during system-wide power 63 transitions (eg. suspend to RAM, hibernation). 64 65 All devices have one of the following two values for the 66 power/async file: 67 68 + "enabled\n" to permit the asynchronous suspend/resume; 69 + "disabled\n" to forbid it; 70 71 The value of this attribute may be changed by writing either 72 "enabled", or "disabled" to it. 73 74 It generally is unsafe to permit the asynchronous suspend/resume 75 of a device unless it is certain that all of the PM dependencies 76 of the device are known to the PM core. However, for some 77 devices this attribute is set to "enabled" by bus type code or 78 device drivers and in that cases it should be safe to leave the 79 default value. 80 81What: /sys/devices/.../power/wakeup_count 82Date: September 2010 83Contact: Rafael J. Wysocki <rjw@sisk.pl> 84Description: 85 The /sys/devices/.../wakeup_count attribute contains the number 86 of signaled wakeup events associated with the device. This 87 attribute is read-only. If the device is not enabled to wake up 88 the system from sleep states, this attribute is empty. 89 90What: /sys/devices/.../power/wakeup_active_count 91Date: September 2010 92Contact: Rafael J. Wysocki <rjw@sisk.pl> 93Description: 94 The /sys/devices/.../wakeup_active_count attribute contains the 95 number of times the processing of wakeup events associated with 96 the device was completed (at the kernel level). This attribute 97 is read-only. If the device is not enabled to wake up the 98 system from sleep states, this attribute is empty. 99 100What: /sys/devices/.../power/wakeup_hit_count 101Date: September 2010 102Contact: Rafael J. Wysocki <rjw@sisk.pl> 103Description: 104 The /sys/devices/.../wakeup_hit_count attribute contains the 105 number of times the processing of a wakeup event associated with 106 the device might prevent the system from entering a sleep state. 107 This attribute is read-only. If the device is not enabled to 108 wake up the system from sleep states, this attribute is empty. 109 110What: /sys/devices/.../power/wakeup_active 111Date: September 2010 112Contact: Rafael J. Wysocki <rjw@sisk.pl> 113Description: 114 The /sys/devices/.../wakeup_active attribute contains either 1, 115 or 0, depending on whether or not a wakeup event associated with 116 the device is being processed (1). This attribute is read-only. 117 If the device is not enabled to wake up the system from sleep 118 states, this attribute is empty. 119 120What: /sys/devices/.../power/wakeup_total_time_ms 121Date: September 2010 122Contact: Rafael J. Wysocki <rjw@sisk.pl> 123Description: 124 The /sys/devices/.../wakeup_total_time_ms attribute contains 125 the total time of processing wakeup events associated with the 126 device, in milliseconds. This attribute is read-only. If the 127 device is not enabled to wake up the system from sleep states, 128 this attribute is empty. 129 130What: /sys/devices/.../power/wakeup_max_time_ms 131Date: September 2010 132Contact: Rafael J. Wysocki <rjw@sisk.pl> 133Description: 134 The /sys/devices/.../wakeup_max_time_ms attribute contains 135 the maximum time of processing a single wakeup event associated 136 with the device, in milliseconds. This attribute is read-only. 137 If the device is not enabled to wake up the system from sleep 138 states, this attribute is empty. 139 140What: /sys/devices/.../power/wakeup_last_time_ms 141Date: September 2010 142Contact: Rafael J. Wysocki <rjw@sisk.pl> 143Description: 144 The /sys/devices/.../wakeup_last_time_ms attribute contains 145 the value of the monotonic clock corresponding to the time of 146 signaling the last wakeup event associated with the device, in 147 milliseconds. This attribute is read-only. If the device is 148 not enabled to wake up the system from sleep states, this 149 attribute is empty. 150 151What: /sys/devices/.../power/autosuspend_delay_ms 152Date: September 2010 153Contact: Alan Stern <stern@rowland.harvard.edu> 154Description: 155 The /sys/devices/.../power/autosuspend_delay_ms attribute 156 contains the autosuspend delay value (in milliseconds). Some 157 drivers do not want their device to suspend as soon as it 158 becomes idle at run time; they want the device to remain 159 inactive for a certain minimum period of time first. That 160 period is called the autosuspend delay. Negative values will 161 prevent the device from being suspended at run time (similar 162 to writing "on" to the power/control attribute). Values >= 163 1000 will cause the autosuspend timer expiration to be rounded 164 up to the nearest second. 165 166 Not all drivers support this attribute. If it isn't supported, 167 attempts to read or write it will yield I/O errors. 168