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 * wakeup - Report/change current wakeup option for device 11 * 12 * Some devices support "wakeup" events, which are hardware signals 13 * used to activate devices from suspended or low power states. Such 14 * devices have one of three values for the sysfs power/wakeup file: 15 * 16 * + "enabled\n" to issue the events; 17 * + "disabled\n" not to do so; or 18 * + "\n" for temporary or permanent inability to issue wakeup. 19 * 20 * (For example, unconfigured USB devices can't issue wakeups.) 21 * 22 * Familiar examples of devices that can issue wakeup events include 23 * keyboards and mice (both PS2 and USB styles), power buttons, modems, 24 * "Wake-On-LAN" Ethernet links, GPIO lines, and more. Some events 25 * will wake the entire system from a suspend state; others may just 26 * wake up the device (if the system as a whole is already active). 27 * Some wakeup events use normal IRQ lines; other use special out 28 * of band signaling. 29 * 30 * It is the responsibility of device drivers to enable (or disable) 31 * wakeup signaling as part of changing device power states, respecting 32 * the policy choices provided through the driver model. 33 * 34 * Devices may not be able to generate wakeup events from all power 35 * states. Also, the events may be ignored in some configurations; 36 * for example, they might need help from other devices that aren't 37 * active, or which may have wakeup disabled. Some drivers rely on 38 * wakeup events internally (unless they are disabled), keeping 39 * their hardware in low power modes whenever they're unused. This 40 * saves runtime power, without requiring system-wide sleep states. 41 */ 42 43 static const char enabled[] = "enabled"; 44 static const char disabled[] = "disabled"; 45 46 static ssize_t 47 wake_show(struct device * dev, struct device_attribute *attr, char * buf) 48 { 49 return sprintf(buf, "%s\n", device_can_wakeup(dev) 50 ? (device_may_wakeup(dev) ? enabled : disabled) 51 : ""); 52 } 53 54 static ssize_t 55 wake_store(struct device * dev, struct device_attribute *attr, 56 const char * buf, size_t n) 57 { 58 char *cp; 59 int len = n; 60 61 if (!device_can_wakeup(dev)) 62 return -EINVAL; 63 64 cp = memchr(buf, '\n', n); 65 if (cp) 66 len = cp - buf; 67 if (len == sizeof enabled - 1 68 && strncmp(buf, enabled, sizeof enabled - 1) == 0) 69 device_set_wakeup_enable(dev, 1); 70 else if (len == sizeof disabled - 1 71 && strncmp(buf, disabled, sizeof disabled - 1) == 0) 72 device_set_wakeup_enable(dev, 0); 73 else 74 return -EINVAL; 75 return n; 76 } 77 78 static DEVICE_ATTR(wakeup, 0644, wake_show, wake_store); 79 80 81 static struct attribute * power_attrs[] = { 82 &dev_attr_wakeup.attr, 83 NULL, 84 }; 85 static struct attribute_group pm_attr_group = { 86 .name = "power", 87 .attrs = power_attrs, 88 }; 89 90 int dpm_sysfs_add(struct device * dev) 91 { 92 return sysfs_create_group(&dev->kobj, &pm_attr_group); 93 } 94 95 void dpm_sysfs_remove(struct device * dev) 96 { 97 sysfs_remove_group(&dev->kobj, &pm_attr_group); 98 } 99