thermal的gov_bang_bang governer

thermal gover 有五种，我们这里以gov_bang_bang.c 为例gov_bang_bang是控制风扇的。之后两种状态，即风扇开和关，并没有提供调整风扇转速的方法.static struct thermal_governor thermal_gov_bang_bang = {.name= "bang_bang",.throttle= bang_bang_control,};int thermal_gov_bang_bang_register(void){return thermal_register_governor(&thermal_gov_bang_bang);}thermal_governor的标准写法，可以看到gov本身也提供了bind_to_tz和unbind_from_tz 两个函数指针，但是一般在定义gov的时候只赋值name和throttle，因为zone device注册的时候已经绑定到cool device了struct thermal_governor {char name[THERMAL_NAME_LENGTH];int (*bind_to_tz)(struct thermal_zone_device *tz);void (*unbind_from_tz)(struct thermal_zone_device *tz);int (*throttle)(struct thermal_zone_device *tz, int trip);struct list_headgovernor_list;};这里的throttle 就是gov针对sensor得到的zone device的温度高或者低作出的调整.来看看控制函数throttlestatic int bang_bang_control(struct thermal_zone_device *tz, int trip){struct thermal_instance *instance;//主要是得到下一步需要执行cool device的状态，本里中的状态有两个，即1或者0.来表示风扇的开和关thermal_zone_trip_update(tz, trip);mutex_lock(&tz->lock);// 开始控制风扇的开或者关list_for_each_entry(instance, &tz->thermal_instances, tz_node)thermal_cdev_update(instance->cdev);mutex_unlock(&tz->lock);return 0;}static void thermal_zone_trip_update(struct thermal_zone_device *tz, int trip){int trip_temp, trip_hyst;struct thermal_instance *instance;//得到触发点的温度tz->ops->get_trip_temp(tz, trip, &trip_temp);if (!tz->ops->get_trip_hyst) {pr_warn_once("Undefined get_trip_hyst for thermal zone %s - ""running with default hysteresis zero\n", tz->type);trip_hyst = 0;} else//得通过zone device的sensor得到目前的温度tz->ops->get_trip_hyst(tz, trip, &trip_hyst);dev_dbg(&tz->device, "Trip%d[temp=%d]:temp=%d:hyst=%d\n",trip, trip_temp, tz->temperature,trip_hyst);mutex_lock(&tz->lock);list_for_each_entry(instance, &tz->thermal_instances, tz_node) {if (instance->trip != trip)continue;/* in case fan is in initial state, switch the fan off */if (instance->target == THERMAL_NO_TARGET)instance->target = 0;/* in case fan is neither on nor off set the fan to active */if (instance->target != 0 && instance->target != 1) {pr_warn("Thermal instance %s controlled by bang-bang has unexpected state: %ld\n",instance->name, instance->target);instance->target = 1;}/* * enable fan when temperature exceeds trip_temp and disable * the fan in case it falls below trip_temp minus hysteresis *///这里是判断的核心，如果目前得到的温度，已经大于触发点的温度了，说明zone device已经过热了，需要开启风扇，当前前提条件是风扇是关的if (instance->target == 0 && tz->temperature >= trip_temp)instance->target = 1;else if (instance->target == 1 &&tz->temperature <= trip_temp - trip_hyst)instance->target = 0;dev_dbg(&instance->cdev->device, "target=%d\n",(int)instance->target);//从list_for_each_entry 来是到这里主要决定instance->target是0还是1.来决定需要设施风扇是关还是开mutex_lock(&instance->cdev->lock);instance->cdev->updated = false; /* cdev needs update */mutex_unlock(&instance->cdev->lock);}mutex_unlock(&tz->lock);}从thermal_zone_trip_update的到instance->target 后就要调用bang_bang_control函数中的list_for_each_entry(instance, &tz->thermal_instances, tz_node)thermal_cdev_update(instance->cdev);来实际控制风扇void thermal_cdev_update(struct thermal_cooling_device *cdev){struct thermal_instance *instance;unsigned long target = 0;mutex_lock(&cdev->lock);/* cooling device is updated*/if (cdev->updated) {mutex_unlock(&cdev->lock);return;}/* Make sure cdev enters the deepest cooling state */list_for_each_entry(instance, &cdev->thermal_instances, cdev_node) {dev_dbg(&cdev->device, "zone%d->target=%lu\n",instance->tz->id, instance->target);if (instance->target == THERMAL_NO_TARGET)continue;if (instance->target > target)target = instance->target;}//核心是这句cdev->ops->set_cur_state(cdev, target);cdev->updated = true;mutex_unlock(&cdev->lock);trace_cdev_update(cdev, target);dev_dbg(&cdev->device, "set to state %lu\n", target);}风扇作为cool device是在drivers/acpi/fan.c中定义的static const struct thermal_cooling_device_ops fan_cooling_ops = {.get_max_state = fan_get_max_state,.get_cur_state = fan_get_cur_state,.set_cur_state = fan_set_cur_state,};可以看到关键的code是fan_set_cur_statestatic intfan_set_cur_state(struct thermal_cooling_device *cdev, unsigned long state){struct acpi_device *device = cdev->devdata;struct acpi_fan *fan = acpi_driver_data(device);if (fan->acpi4)return fan_set_state_acpi4(device, state);elsereturn fan_set_state(device, state); }假如这里fan->acpi4为0,则static int fan_set_state(struct acpi_device *device, unsigned long state){if (state != 0 && state != 1)return -EINVAL;//可见最终通过acpi_device_set_power 来设置fan device是ACPI_STATE_D0（开风扇） 还是 ACPI_STATE_D3_COLDreturn acpi_device_set_power(device,     state ? ACPI_STATE_D0 : ACPI_STATE_D3_COLD);}