What: /sys/devices/.../power/ Date: January 2009 Contact: Rafael J. Wysocki Description: The /sys/devices/.../power directory contains attributes allowing the user space to check and modify some power management related properties of given device. What: /sys/devices/.../power/wakeup Date: January 2009 Contact: Rafael J. Wysocki Description: The /sys/devices/.../power/wakeup attribute allows the user space to check if the device is enabled to wake up the system from sleep states, such as the memory sleep state (suspend to RAM) and hibernation (suspend to disk), and to enable or disable it to do that as desired. Some devices support "wakeup" events, which are hardware signals used to activate the system from a sleep state. Such devices have one of the following two values for the sysfs power/wakeup file: + "enabled\n" to issue the events; + "disabled\n" not to do so; In that cases the user space can change the setting represented by the contents of this file by writing either "enabled", or "disabled" to it. For the devices that are not capable of generating system wakeup events this file is not present. In that case the device cannot be enabled to wake up the system from sleep states. What: /sys/devices/.../power/control Date: January 2009 Contact: Rafael J. Wysocki Description: The /sys/devices/.../power/control attribute allows the user space to control the run-time power management of the device. All devices have one of the following two values for the power/control file: + "auto\n" to allow the device to be power managed at run time; + "on\n" to prevent the device from being power managed; The default for all devices is "auto", which means that they may be subject to automatic power management, depending on their drivers. Changing this attribute to "on" prevents the driver from power managing the device at run time. Doing that while the device is suspended causes it to be woken up. What: /sys/devices/.../power/async Date: January 2009 Contact: Rafael J. Wysocki Description: The /sys/devices/.../async attribute allows the user space to enable or diasble the device's suspend and resume callbacks to be executed asynchronously (ie. in separate threads, in parallel with the main suspend/resume thread) during system-wide power transitions (eg. suspend to RAM, hibernation). All devices have one of the following two values for the power/async file: + "enabled\n" to permit the asynchronous suspend/resume; + "disabled\n" to forbid it; The value of this attribute may be changed by writing either "enabled", or "disabled" to it. It generally is unsafe to permit the asynchronous suspend/resume of a device unless it is certain that all of the PM dependencies of the device are known to the PM core. However, for some devices this attribute is set to "enabled" by bus type code or device drivers and in that cases it should be safe to leave the default value. What: /sys/devices/.../power/wakeup_count Date: September 2010 Contact: Rafael J. Wysocki Description: The /sys/devices/.../wakeup_count attribute contains the number of signaled wakeup events associated with the device. This attribute is read-only. If the device is not enabled to wake up the system from sleep states, this attribute is not present. What: /sys/devices/.../power/wakeup_active_count Date: September 2010 Contact: Rafael J. Wysocki Description: The /sys/devices/.../wakeup_active_count attribute contains the number of times the processing of wakeup events associated with the device was completed (at the kernel level). This attribute is read-only. If the device is not enabled to wake up the system from sleep states, this attribute is not present. What: /sys/devices/.../power/wakeup_hit_count Date: September 2010 Contact: Rafael J. Wysocki Description: The /sys/devices/.../wakeup_hit_count attribute contains the number of times the processing of a wakeup event associated with the device might prevent the system from entering a sleep state. This attribute is read-only. If the device is not enabled to wake up the system from sleep states, this attribute is not present. What: /sys/devices/.../power/wakeup_active Date: September 2010 Contact: Rafael J. Wysocki Description: The /sys/devices/.../wakeup_active attribute contains either 1, or 0, depending on whether or not a wakeup event associated with the device is being processed (1). This attribute is read-only. If the device is not enabled to wake up the system from sleep states, this attribute is not present. What: /sys/devices/.../power/wakeup_total_time_ms Date: September 2010 Contact: Rafael J. Wysocki Description: The /sys/devices/.../wakeup_total_time_ms attribute contains the total time of processing wakeup events associated with the device, in milliseconds. This attribute is read-only. If the device is not enabled to wake up the system from sleep states, this attribute is not present. What: /sys/devices/.../power/wakeup_max_time_ms Date: September 2010 Contact: Rafael J. Wysocki Description: The /sys/devices/.../wakeup_max_time_ms attribute contains the maximum time of processing a single wakeup event associated with the device, in milliseconds. This attribute is read-only. If the device is not enabled to wake up the system from sleep states, this attribute is not present. What: /sys/devices/.../power/wakeup_last_time_ms Date: September 2010 Contact: Rafael J. Wysocki Description: The /sys/devices/.../wakeup_last_time_ms attribute contains the value of the monotonic clock corresponding to the time of signaling the last wakeup event associated with the device, in milliseconds. This attribute is read-only. If the device is not enabled to wake up the system from sleep states, this attribute is not present. What: /sys/devices/.../power/autosuspend_delay_ms Date: September 2010 Contact: Alan Stern Description: The /sys/devices/.../power/autosuspend_delay_ms attribute contains the autosuspend delay value (in milliseconds). Some drivers do not want their device to suspend as soon as it becomes idle at run time; they want the device to remain inactive for a certain minimum period of time first. That period is called the autosuspend delay. Negative values will prevent the device from being suspended at run time (similar to writing "on" to the power/control attribute). Values >= 1000 will cause the autosuspend timer expiration to be rounded up to the nearest second. Not all drivers support this attribute. If it isn't supported, attempts to read or write it will yield I/O errors.