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 if (dev->power.power_state.event) 31 return sprintf(buf, "2\n"); 32 else 33 return sprintf(buf, "0\n"); 34 } 35 36 static ssize_t state_store(struct device * dev, struct device_attribute *attr, const char * buf, size_t n) 37 { 38 pm_message_t state; 39 int error = -EINVAL; 40 41 state.event = PM_EVENT_SUSPEND; 42 /* Older apps expected to write "3" here - confused with PCI D3 */ 43 if ((n == 1) && !strcmp(buf, "3")) 44 error = dpm_runtime_suspend(dev, state); 45 46 if ((n == 1) && !strcmp(buf, "2")) 47 error = dpm_runtime_suspend(dev, state); 48 49 if ((n == 1) && !strcmp(buf, "0")) { 50 dpm_runtime_resume(dev); 51 error = 0; 52 } 53 54 return error ? error : n; 55 } 56 57 static DEVICE_ATTR(state, 0644, state_show, state_store); 58 59 60 /* 61 * wakeup - Report/change current wakeup option for device 62 * 63 * Some devices support "wakeup" events, which are hardware signals 64 * used to activate devices from suspended or low power states. Such 65 * devices have one of three values for the sysfs power/wakeup file: 66 * 67 * + "enabled\n" to issue the events; 68 * + "disabled\n" not to do so; or 69 * + "\n" for temporary or permanent inability to issue wakeup. 70 * 71 * (For example, unconfigured USB devices can't issue wakeups.) 72 * 73 * Familiar examples of devices that can issue wakeup events include 74 * keyboards and mice (both PS2 and USB styles), power buttons, modems, 75 * "Wake-On-LAN" Ethernet links, GPIO lines, and more. Some events 76 * will wake the entire system from a suspend state; others may just 77 * wake up the device (if the system as a whole is already active). 78 * Some wakeup events use normal IRQ lines; other use special out 79 * of band signaling. 80 * 81 * It is the responsibility of device drivers to enable (or disable) 82 * wakeup signaling as part of changing device power states, respecting 83 * the policy choices provided through the driver model. 84 * 85 * Devices may not be able to generate wakeup events from all power 86 * states. Also, the events may be ignored in some configurations; 87 * for example, they might need help from other devices that aren't 88 * active, or which may have wakeup disabled. Some drivers rely on 89 * wakeup events internally (unless they are disabled), keeping 90 * their hardware in low power modes whenever they're unused. This 91 * saves runtime power, without requiring system-wide sleep states. 92 */ 93 94 static const char enabled[] = "enabled"; 95 static const char disabled[] = "disabled"; 96 97 static ssize_t 98 wake_show(struct device * dev, struct device_attribute *attr, char * buf) 99 { 100 return sprintf(buf, "%s\n", device_can_wakeup(dev) 101 ? (device_may_wakeup(dev) ? enabled : disabled) 102 : ""); 103 } 104 105 static ssize_t 106 wake_store(struct device * dev, struct device_attribute *attr, 107 const char * buf, size_t n) 108 { 109 char *cp; 110 int len = n; 111 112 if (!device_can_wakeup(dev)) 113 return -EINVAL; 114 115 cp = memchr(buf, '\n', n); 116 if (cp) 117 len = cp - buf; 118 if (len == sizeof enabled - 1 119 && strncmp(buf, enabled, sizeof enabled - 1) == 0) 120 device_set_wakeup_enable(dev, 1); 121 else if (len == sizeof disabled - 1 122 && strncmp(buf, disabled, sizeof disabled - 1) == 0) 123 device_set_wakeup_enable(dev, 0); 124 else 125 return -EINVAL; 126 return n; 127 } 128 129 static DEVICE_ATTR(wakeup, 0644, wake_show, wake_store); 130 131 132 static struct attribute * power_attrs[] = { 133 &dev_attr_state.attr, 134 &dev_attr_wakeup.attr, 135 NULL, 136 }; 137 static struct attribute_group pm_attr_group = { 138 .name = "power", 139 .attrs = power_attrs, 140 }; 141 142 int dpm_sysfs_add(struct device * dev) 143 { 144 return sysfs_create_group(&dev->kobj, &pm_attr_group); 145 } 146 147 void dpm_sysfs_remove(struct device * dev) 148 { 149 sysfs_remove_group(&dev->kobj, &pm_attr_group); 150 } 151