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 * wakeup - Report/change current wakeup option for device 12 * 13 * Some devices support "wakeup" events, which are hardware signals 14 * used to activate devices from suspended or low power states. Such 15 * devices have one of three values for the sysfs power/wakeup file: 16 * 17 * + "enabled\n" to issue the events; 18 * + "disabled\n" not to do so; or 19 * + "\n" for temporary or permanent inability to issue wakeup. 20 * 21 * (For example, unconfigured USB devices can't issue wakeups.) 22 * 23 * Familiar examples of devices that can issue wakeup events include 24 * keyboards and mice (both PS2 and USB styles), power buttons, modems, 25 * "Wake-On-LAN" Ethernet links, GPIO lines, and more. Some events 26 * will wake the entire system from a suspend state; others may just 27 * wake up the device (if the system as a whole is already active). 28 * Some wakeup events use normal IRQ lines; other use special out 29 * of band signaling. 30 * 31 * It is the responsibility of device drivers to enable (or disable) 32 * wakeup signaling as part of changing device power states, respecting 33 * the policy choices provided through the driver model. 34 * 35 * Devices may not be able to generate wakeup events from all power 36 * states. Also, the events may be ignored in some configurations; 37 * for example, they might need help from other devices that aren't 38 * active, or which may have wakeup disabled. Some drivers rely on 39 * wakeup events internally (unless they are disabled), keeping 40 * their hardware in low power modes whenever they're unused. This 41 * saves runtime power, without requiring system-wide sleep states. 42 */ 43 44 static const char enabled[] = "enabled"; 45 static const char disabled[] = "disabled"; 46 47 static ssize_t 48 wake_show(struct device * dev, struct device_attribute *attr, char * buf) 49 { 50 return sprintf(buf, "%s\n", device_can_wakeup(dev) 51 ? (device_may_wakeup(dev) ? enabled : disabled) 52 : ""); 53 } 54 55 static ssize_t 56 wake_store(struct device * dev, struct device_attribute *attr, 57 const char * buf, size_t n) 58 { 59 char *cp; 60 int len = n; 61 62 if (!device_can_wakeup(dev)) 63 return -EINVAL; 64 65 cp = memchr(buf, '\n', n); 66 if (cp) 67 len = cp - buf; 68 if (len == sizeof enabled - 1 69 && strncmp(buf, enabled, sizeof enabled - 1) == 0) 70 device_set_wakeup_enable(dev, 1); 71 else if (len == sizeof disabled - 1 72 && strncmp(buf, disabled, sizeof disabled - 1) == 0) 73 device_set_wakeup_enable(dev, 0); 74 else 75 return -EINVAL; 76 return n; 77 } 78 79 static DEVICE_ATTR(wakeup, 0644, wake_show, wake_store); 80 81 82 static struct attribute * power_attrs[] = { 83 &dev_attr_wakeup.attr, 84 NULL, 85 }; 86 static struct attribute_group pm_attr_group = { 87 .name = "power", 88 .attrs = power_attrs, 89 }; 90 91 int dpm_sysfs_add(struct device * dev) 92 { 93 return sysfs_create_group(&dev->kobj, &pm_attr_group); 94 } 95 96 void dpm_sysfs_remove(struct device * dev) 97 { 98 sysfs_remove_group(&dev->kobj, &pm_attr_group); 99 } 100