1 /* 2 * drivers/base/power/sysfs.c - sysfs entries for device PM 3 */ 4 5 #include <linux/device.h> 6 #include <linux/string.h> 7 #include "power.h" 8 9 10 /** 11 * state - Control current power state of device 12 * 13 * show() returns the current power state of the device. '0' indicates 14 * the device is on. Other values (1-3) indicate the device is in a low 15 * power state. 16 * 17 * store() sets the current power state, which is an integer value 18 * between 0-3. If the device is on ('0'), and the value written is 19 * greater than 0, then the device is placed directly into the low-power 20 * state (via its driver's ->suspend() method). 21 * If the device is currently in a low-power state, and the value is 0, 22 * the device is powered back on (via the ->resume() method). 23 * If the device is in a low-power state, and a different low-power state 24 * is requested, the device is first resumed, then suspended into the new 25 * low-power state. 26 */ 27 28 static ssize_t state_show(struct device * dev, struct device_attribute *attr, char * buf) 29 { 30 return sprintf(buf, "%u\n", dev->power.power_state.event); 31 } 32 33 static ssize_t state_store(struct device * dev, struct device_attribute *attr, const char * buf, size_t n) 34 { 35 pm_message_t state; 36 char * rest; 37 int error = 0; 38 39 state.event = simple_strtoul(buf, &rest, 10); 40 if (*rest) 41 return -EINVAL; 42 if (state.event) 43 error = dpm_runtime_suspend(dev, state); 44 else 45 dpm_runtime_resume(dev); 46 return error ? error : n; 47 } 48 49 static DEVICE_ATTR(state, 0644, state_show, state_store); 50 51 52 /* 53 * wakeup - Report/change current wakeup option for device 54 * 55 * Some devices support "wakeup" events, which are hardware signals 56 * used to activate devices from suspended or low power states. Such 57 * devices have one of three values for the sysfs power/wakeup file: 58 * 59 * + "enabled\n" to issue the events; 60 * + "disabled\n" not to do so; or 61 * + "\n" for temporary or permanent inability to issue wakeup. 62 * 63 * (For example, unconfigured USB devices can't issue wakeups.) 64 * 65 * Familiar examples of devices that can issue wakeup events include 66 * keyboards and mice (both PS2 and USB styles), power buttons, modems, 67 * "Wake-On-LAN" Ethernet links, GPIO lines, and more. Some events 68 * will wake the entire system from a suspend state; others may just 69 * wake up the device (if the system as a whole is already active). 70 * Some wakeup events use normal IRQ lines; other use special out 71 * of band signaling. 72 * 73 * It is the responsibility of device drivers to enable (or disable) 74 * wakeup signaling as part of changing device power states, respecting 75 * the policy choices provided through the driver model. 76 * 77 * Devices may not be able to generate wakeup events from all power 78 * states. Also, the events may be ignored in some configurations; 79 * for example, they might need help from other devices that aren't 80 * active, or which may have wakeup disabled. Some drivers rely on 81 * wakeup events internally (unless they are disabled), keeping 82 * their hardware in low power modes whenever they're unused. This 83 * saves runtime power, without requiring system-wide sleep states. 84 */ 85 86 static const char enabled[] = "enabled"; 87 static const char disabled[] = "disabled"; 88 89 static ssize_t 90 wake_show(struct device * dev, struct device_attribute *attr, char * buf) 91 { 92 return sprintf(buf, "%s\n", device_can_wakeup(dev) 93 ? (device_may_wakeup(dev) ? enabled : disabled) 94 : ""); 95 } 96 97 static ssize_t 98 wake_store(struct device * dev, struct device_attribute *attr, 99 const char * buf, size_t n) 100 { 101 char *cp; 102 int len = n; 103 104 if (!device_can_wakeup(dev)) 105 return -EINVAL; 106 107 cp = memchr(buf, '\n', n); 108 if (cp) 109 len = cp - buf; 110 if (len == sizeof enabled - 1 111 && strncmp(buf, enabled, sizeof enabled - 1) == 0) 112 device_set_wakeup_enable(dev, 1); 113 else if (len == sizeof disabled - 1 114 && strncmp(buf, disabled, sizeof disabled - 1) == 0) 115 device_set_wakeup_enable(dev, 0); 116 else 117 return -EINVAL; 118 return n; 119 } 120 121 static DEVICE_ATTR(wakeup, 0644, wake_show, wake_store); 122 123 124 static struct attribute * power_attrs[] = { 125 &dev_attr_state.attr, 126 &dev_attr_wakeup.attr, 127 NULL, 128 }; 129 static struct attribute_group pm_attr_group = { 130 .name = "power", 131 .attrs = power_attrs, 132 }; 133 134 int dpm_sysfs_add(struct device * dev) 135 { 136 return sysfs_create_group(&dev->kobj, &pm_attr_group); 137 } 138 139 void dpm_sysfs_remove(struct device * dev) 140 { 141 sysfs_remove_group(&dev->kobj, &pm_attr_group); 142 } 143