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971cb7fb RW |
1 | What: /sys/devices/.../power/ |
2 | Date: January 2009 | |
3 | Contact: Rafael J. Wysocki <rjw@sisk.pl> | |
4 | Description: | |
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 | ||
9 | What: /sys/devices/.../power/wakeup | |
10 | Date: January 2009 | |
11 | Contact: Rafael J. Wysocki <rjw@sisk.pl> | |
12 | Description: | |
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 | ||
36 | What: /sys/devices/.../power/control | |
37 | Date: January 2009 | |
38 | Contact: Rafael J. Wysocki <rjw@sisk.pl> | |
39 | Description: | |
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. | |
5a2eb858 RW |
54 | |
55 | What: /sys/devices/.../power/async | |
56 | Date: January 2009 | |
57 | Contact: Rafael J. Wysocki <rjw@sisk.pl> | |
58 | Description: | |
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. | |
074037ec RW |
80 | |
81 | What: /sys/devices/.../power/wakeup_count | |
82 | Date: September 2010 | |
83 | Contact: Rafael J. Wysocki <rjw@sisk.pl> | |
84 | Description: | |
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 | ||
90 | What: /sys/devices/.../power/wakeup_active_count | |
91 | Date: September 2010 | |
92 | Contact: Rafael J. Wysocki <rjw@sisk.pl> | |
93 | Description: | |
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 | ||
100 | What: /sys/devices/.../power/wakeup_hit_count | |
101 | Date: September 2010 | |
102 | Contact: Rafael J. Wysocki <rjw@sisk.pl> | |
103 | Description: | |
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 | ||
110 | What: /sys/devices/.../power/wakeup_active | |
111 | Date: September 2010 | |
112 | Contact: Rafael J. Wysocki <rjw@sisk.pl> | |
113 | Description: | |
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 | ||
120 | What: /sys/devices/.../power/wakeup_total_time_ms | |
121 | Date: September 2010 | |
122 | Contact: Rafael J. Wysocki <rjw@sisk.pl> | |
123 | Description: | |
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 | ||
130 | What: /sys/devices/.../power/wakeup_max_time_ms | |
131 | Date: September 2010 | |
132 | Contact: Rafael J. Wysocki <rjw@sisk.pl> | |
133 | Description: | |
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 | ||
140 | What: /sys/devices/.../power/wakeup_last_time_ms | |
141 | Date: September 2010 | |
142 | Contact: Rafael J. Wysocki <rjw@sisk.pl> | |
143 | Description: | |
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. | |
15bcb91d AS |
150 | |
151 | What: /sys/devices/.../power/autosuspend_delay_ms | |
152 | Date: September 2010 | |
153 | Contact: Alan Stern <stern@rowland.harvard.edu> | |
154 | Description: | |
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. |