1 /* 2 * drivers/base/power/sysfs.c - sysfs entries for device PM 3 */ 4 5 #include <linux/device.h> 6 #include "power.h" 7 8 9 /** 10 * state - Control current power state of device 11 * 12 * show() returns the current power state of the device. '0' indicates 13 * the device is on. Other values (1-3) indicate the device is in a low 14 * power state. 15 * 16 * store() sets the current power state, which is an integer value 17 * between 0-3. If the device is on ('0'), and the value written is 18 * greater than 0, then the device is placed directly into the low-power 19 * state (via its driver's ->suspend() method). 20 * If the device is currently in a low-power state, and the value is 0, 21 * the device is powered back on (via the ->resume() method). 22 * If the device is in a low-power state, and a different low-power state 23 * is requested, the device is first resumed, then suspended into the new 24 * low-power state. 25 */ 26 27 static ssize_t state_show(struct device * dev, struct device_attribute *attr, char * buf) 28 { 29 return sprintf(buf, "%u\n", dev->power.power_state.event); 30 } 31 32 static ssize_t state_store(struct device * dev, struct device_attribute *attr, const char * buf, size_t n) 33 { 34 pm_message_t state; 35 char * rest; 36 int error = 0; 37 38 state.event = simple_strtoul(buf, &rest, 10); 39 if (*rest) 40 return -EINVAL; 41 if (state.event) 42 error = dpm_runtime_suspend(dev, state); 43 else 44 dpm_runtime_resume(dev); 45 return error ? error : n; 46 } 47 48 static DEVICE_ATTR(state, 0644, state_show, state_store); 49 50 51 /* 52 * wakeup - Report/change current wakeup option for device 53 * 54 * Some devices support "wakeup" events, which are hardware signals 55 * used to activate devices from suspended or low power states. Such 56 * devices have one of three values for the sysfs power/wakeup file: 57 * 58 * + "enabled\n" to issue the events; 59 * + "disabled\n" not to do so; or 60 * + "\n" for temporary or permanent inability to issue wakeup. 61 * 62 * (For example, unconfigured USB devices can't issue wakeups.) 63 * 64 * Familiar examples of devices that can issue wakeup events include 65 * keyboards and mice (both PS2 and USB styles), power buttons, modems, 66 * "Wake-On-LAN" Ethernet links, GPIO lines, and more. Some events 67 * will wake the entire system from a suspend state; others may just 68 * wake up the device (if the system as a whole is already active). 69 * Some wakeup events use normal IRQ lines; other use special out 70 * of band signaling. 71 * 72 * It is the responsibility of device drivers to enable (or disable) 73 * wakeup signaling as part of changing device power states, respecting 74 * the policy choices provided through the driver model. 75 * 76 * Devices may not be able to generate wakeup events from all power 77 * states. Also, the events may be ignored in some configurations; 78 * for example, they might need help from other devices that aren't 79 * active, or which may have wakeup disabled. Some drivers rely on 80 * wakeup events internally (unless they are disabled), keeping 81 * their hardware in low power modes whenever they're unused. This 82 * saves runtime power, without requiring system-wide sleep states. 83 */ 84 85 static const char enabled[] = "enabled"; 86 static const char disabled[] = "disabled"; 87 88 static ssize_t 89 wake_show(struct device * dev, struct device_attribute *attr, char * buf) 90 { 91 return sprintf(buf, "%s\n", device_can_wakeup(dev) 92 ? (device_may_wakeup(dev) ? enabled : disabled) 93 : ""); 94 } 95 96 static ssize_t 97 wake_store(struct device * dev, struct device_attribute *attr, 98 const char * buf, size_t n) 99 { 100 char *cp; 101 int len = n; 102 103 if (!device_can_wakeup(dev)) 104 return -EINVAL; 105 106 cp = memchr(buf, '\n', n); 107 if (cp) 108 len = cp - buf; 109 if (len == sizeof enabled - 1 110 && strncmp(buf, enabled, sizeof enabled - 1) == 0) 111 device_set_wakeup_enable(dev, 1); 112 else if (len == sizeof disabled - 1 113 && strncmp(buf, disabled, sizeof disabled - 1) == 0) 114 device_set_wakeup_enable(dev, 0); 115 else 116 return -EINVAL; 117 return n; 118 } 119 120 static DEVICE_ATTR(wakeup, 0644, wake_show, wake_store); 121 122 123 static struct attribute * power_attrs[] = { 124 &dev_attr_state.attr, 125 &dev_attr_wakeup.attr, 126 NULL, 127 }; 128 static struct attribute_group pm_attr_group = { 129 .name = "power", 130 .attrs = power_attrs, 131 }; 132 133 int dpm_sysfs_add(struct device * dev) 134 { 135 return sysfs_create_group(&dev->kobj, &pm_attr_group); 136 } 137 138 void dpm_sysfs_remove(struct device * dev) 139 { 140 sysfs_remove_group(&dev->kobj, &pm_attr_group); 141 } 142