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, char * buf) 28 { 29 return sprintf(buf, "%u\n", dev->power.power_state); 30 } 31 32 static ssize_t state_store(struct device * dev, const char * buf, size_t n) 33 { 34 u32 state; 35 char * rest; 36 int error = 0; 37 38 state = simple_strtoul(buf, &rest, 10); 39 if (*rest) 40 return -EINVAL; 41 if (state) 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 static struct attribute * power_attrs[] = { 52 &dev_attr_state.attr, 53 NULL, 54 }; 55 static struct attribute_group pm_attr_group = { 56 .name = "power", 57 .attrs = power_attrs, 58 }; 59 60 int dpm_sysfs_add(struct device * dev) 61 { 62 return sysfs_create_group(&dev->kobj, &pm_attr_group); 63 } 64 65 void dpm_sysfs_remove(struct device * dev) 66 { 67 sysfs_remove_group(&dev->kobj, &pm_attr_group); 68 } 69