linux kernel power source

main.c

power_attr(pm_async);
#ifdef CONFIG_SUSPEND
static ssize_t mem_sleep_show(struct kobject *kobj, struct kobj_attribute *attr,char *buf){
	char *s = buf;
	suspend_state_t i;
	for (i = PM_SUSPEND_MIN; i < PM_SUSPEND_MAX; i++)
		if (mem_sleep_states[i]) {
			const char *label = mem_sleep_states[i];
			if (mem_sleep_current == i)
				s += sprintf(s, "[%s] ", label);
			else
				s += sprintf(s, "%s ", label);
	}
	if (s != buf)
		*(s-1) = '\n';
	return (s - buf);
}
static suspend_state_t decode_suspend_state(const char *buf, size_t n){
	suspend_state_t state;
	char *p;
	int len;
	p = memchr(buf, '\n', n);
	len = p ? p - buf : n;
	for (state = PM_SUSPEND_MIN; state < PM_SUSPEND_MAX; state++) {
		const char *label = mem_sleep_states[state];
		if (label && len == strlen(label) && !strncmp(buf, label, len))
			return state;
	}
	return PM_SUSPEND_ON;
}