thermal中cool device和zone device的绑定

thermal是linux中温度相关的子模块，其源码在drivers/thermal/。thermal子系统分为thermal zone device和thermal cool device。zone device是获取当前设备温度的设备，例如传感器等。
在kernel中用来thermal_zone_device代表zone devie。
struct thermal_zone_device {
	int id;
	char type[THERMAL_NAME_LENGTH];
	struct thermal_zone_device_ops *ops;
	struct thermal_zone_params *tzp;
	struct thermal_governor *governor;
};
其成员变量thermal_zone_device_ops 代表zone device 获取温度的方法
struct thermal_zone_device_ops {
	int (*bind) (struct thermal_zone_device *,
		     struct thermal_cooling_device *);
	int (*unbind) (struct thermal_zone_device *,
		       struct thermal_cooling_device *);
	int (*get_temp) (struct thermal_zone_device *, int *);
	int (*set_trips) (struct thermal_zone_device *, int, int);
};
其最终要的成员变量是get_temp，来得到zone device的当前温度
thermal_cooling_device代表降温的手段，对风扇而言就是提高转速，对cpu而言就是降压降频来减少cpu的发热
struct thermal_cooling_device {
	const struct thermal_cooling_device_ops *ops;
};

struct thermal_cooling_device_ops {
	int (*get_max_state) (struct thermal_cooling_device *, unsigned long *);
	int (*get_cur_state) (struct thermal_cooling_device *, unsigned long *);
	int (*set_cur_state) (struct thermal_cooling_device *, unsigned long);
};

类似其成员变量thermal_cooling_device_ops 中的set_cur_state代表当前需要降温的等级
还有一个Thermal Governor代表降温的策略。从makefile中可以发现，总共有如下五种Governor
# governors
thermal_sys-$(CONFIG_THERMAL_GOV_FAIR_SHARE)	+= fair_share.o
thermal_sys-$(CONFIG_THERMAL_GOV_BANG_BANG)	+= gov_bang_bang.o
thermal_sys-$(CONFIG_THERMAL_GOV_STEP_WISE)	+= step_wise.o
thermal_sys-$(CONFIG_THERMAL_GOV_USER_SPACE)	+= user_space.o
thermal_sys-$(CONFIG_THERMAL_GOV_POWER_ALLOCATOR)	+= power_allocator.o
从下面的makefile可以看出thermal的初始化文件是thermal_core.c
thermal_sys-y			+= thermal_core.o thermal_sysfs.o \
					thermal_helpers.o

fs_initcall(thermal_init);
可见开机会通过fs_initcall调用thermal_init。

thermal_init->thermal_register_governors
5中governors 会同时存在系统中
static int __init thermal_register_governors(void)
{
	int result;

	result = thermal_gov_step_wise_register();
	if (result)
		return result;

	result = thermal_gov_fair_share_register();
	if (result)
		return result;

	result = thermal_gov_bang_bang_register();
	if (result)
		return result;

	result = thermal_gov_user_space_register();
	if (result)
		return result;

	return thermal_gov_power_allocator_register();
}
thermal_init->of_parse_thermal_zones
int __init of_parse_thermal_zones(void)
{
	struct device_node *np, *child;
	struct __thermal_zone *tz;
	struct thermal_zone_device_ops *ops;

	np = of_find_node_by_name(NULL, "thermal-zones");
	if (!np) {
		pr_debug("unable to find thermal zones\n");
		return 0; /* Run successfully on systems without thermal DT */
	}

	for_each_available_child_of_node(np, child) {
		struct thermal_zone_device *zone;
		struct thermal_zone_params *tzp;
		int i, mask = 0;
		u32 prop;
//通过devicetree 得到__thermal_zone
		tz = thermal_of_build_thermal_zone(child);
		if (IS_ERR(tz)) {
			pr_err("failed to build thermal zone %s: %ld\n",
			       child->name,
			       PTR_ERR(tz));
			continue;
		}

		ops = kmemdup(&of_thermal_ops, sizeof(*ops), GFP_KERNEL);
		if (!ops)
			goto exit_free;

		tzp = kzalloc(sizeof(*tzp), GFP_KERNEL);
		if (!tzp) {
			kfree(ops);
			goto exit_free;
		}

		/* No hwmon because there might be hwmon drivers registering */
		tzp->no_hwmon = true;

		if (!of_property_read_u32(child, "sustainable-power", &prop))
			tzp->sustainable_power = prop;

		for (i = 0; i < tz->ntrips; i++)
			mask |= 1 << i;

		/* these two are left for temperature drivers to use */
		tzp->slope = tz->slope;
		tzp->offset = tz->offset;
在thermal_zone_device_register->bind_tz->__bind 来让cool device和zone device绑定
		zone = thermal_zone_device_register(child->name, tz->ntrips,
						    mask, tz,
						    ops, tzp,
						    tz->passive_delay,
						    tz->polling_delay);
		if (IS_ERR(zone)) {
			pr_err("Failed to build %s zone %ld\n", child->name,
			       PTR_ERR(zone));
			kfree(tzp);
			kfree(ops);
			of_thermal_free_zone(tz);
			/* attempting to build remaining zones still */
		}
	}
	of_node_put(np);

	return 0;
}

static void __bind(struct thermal_zone_device *tz, int mask,
		   struct thermal_cooling_device *cdev,
		   unsigned long *limits,
		   unsigned int weight)
{
	int i, ret;

	for (i = 0; i < tz->trips; i++) {
		if (mask & (1 << i)) {
			unsigned long upper, lower;

			upper = THERMAL_NO_LIMIT;
			lower = THERMAL_NO_LIMIT;
			if (limits) {
				lower = limits[i * 2];
				upper = limits[i * 2 + 1];
			}
//可以看到最终调用thermal_zone_bind_cooling_device来绑定cool device和zone device 省略中间过程的话，可以看到是起始是在注册zone device函数thermal_zone_device_register中调用thermal_zone_bind_cooling_device来绑定cool device.
thermal_zone_device_register->thermal_zone_bind_cooling_device
			ret = thermal_zone_bind_cooling_device(tz, i, cdev,
							       upper, lower,
							       weight);
			if (ret)
				print_bind_err_msg(tz, cdev, ret);
		}
	}
}