proc 或sys下文件生成方法

/sys 下文件生成：

1. 定义属性,如： /kernel/power/power.h
#define power_attr(_name) \
static struct kobj_attribute _name##_attr = {   \
    .attr   = {             \
        .name = __stringify(_name), \
        .mode = 0644,           \
    },                  \
    .show   = _name##_show,         \
    .store  = _name##_store,        \
}
power_attr(state);  // 定义state属性

2. 如果是多个，可以生成属性组，如：/kernel/power/main.c
static struct attribute * g[] = {
    &state_attr.attr,
#ifdef CONFIG_PM_TRACE
    &pm_trace_attr.attr,
#endif
#ifdef CONFIG_PM_SLEEP
    &pm_async_attr.attr,
#ifdef CONFIG_PM_DEBUG
    &pm_test_attr.attr,
#endif
#endif
    NULL,
};
static struct attribute_group attr_group = {
    .attrs = g,
};

3. 定义操作读写/sys下文件的函数：
static ssize_t state_show(struct kobject *kobj, struct kobj_attribute *attr,
              char *buf)
{
...................
    return (s - buf);
}

static ssize_t state_store(struct kobject *kobj, struct kobj_attribute *attr,
               const char *buf, size_t n)
{
....................
 Exit:
    return error ? error : n;
}
4. 创建文件：

static int __init pm_init(void)
{
    int error = pm_start_workqueue();
    if (error)
        return error;
    power_kobj = kobject_create_and_add("power", NULL);
    if (!power_kobj)
        return -ENOMEM;
    return sysfs_create_group(power_kobj, &attr_group);
}

/proc 下文件的生成方法类似：
1. 定义属性写属性组：
static DEVICE_ATTR(in0_input, S_IRUGO, show_volt, NULL);
static DEVICE_ATTR(curr1_input, S_IRUGO, show_curr, NULL);

static struct attribute *zl6100_attributes[] = {
    &dev_attr_in0_input.attr,
    &dev_attr_curr1_input.attr,
    NULL
};

static const struct attribute_group zl6100_group = {
    .attrs = zl6100_attributes,
};

2. 定义读写文件的函数：
static int show_volt(struct device *dev, struct device_attribute *attr,
        char *buf)
{
.....................
    return sprintf(buf, "%d\n", volt);
}

static int show_curr(struct device *dev, struct device_attribute *attr,
        char *buf)
{
....................
    return sprintf(buf, "%d\n", cur);
}

3. 创建文件：
 err = sysfs_create_group(&client->dev.kobj, &zl6100_group);