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