设备驱动 --- device_driver

最新推荐文章于 2021-08-06 03:17:16 发布

原创最新推荐文章于 2021-08-06 03:17:16 发布 · 527 阅读

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#struct #file #methods #module #table

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本文深入探讨了驱动程序的定义、注册与注销过程，以及如何通过系统属性结构实现驱动程序的配置与管理。详细解释了`device_driver`结构体、`driver_register`与`driver_unregister`函数的作用，并介绍了驱动程序属性的声明与创建方法。

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1. 驱动程序device_driver定义:

    struct device_driver {
        const char        *name;                  //驱动程序名
        struct bus_type        *bus;               //驱动程序所操作的总线类型
        struct module        *owner;
        const char        *mod_name;    /* used for built-in modules */
        bool suppress_bind_attrs;    /* disables bind/unbind via sysfs */
    #if defined(CONFIG_OF)
        const struct of_device_id    *of_match_table;
    #endif
        int (*probe) (struct device *dev);        //probe函数用来查询特定设备是否存在。
        int (*remove) (struct device *dev);      
        void (*shutdown) (struct device *dev);
        int (*suspend) (struct device *dev, pm_message_t state);
        int (*resume) (struct device *dev);
        const struct attribute_group **groups;
        const struct dev_pm_ops *pm;
        struct driver_private *p;
    };

2. device_driver的注册和注销，driver_register()/ driver_unregister():

    /**
     * driver_register - register driver with bus
     * @drv: driver to register
     *
     * We pass off most of the work to the bus_add_driver() call,
     * since most of the things we have to do deal with the bus
     * structures.
     */
    int driver_register(struct device_driver *drv)
    {
        int ret;
        struct device_driver *other;
        BUG_ON(!drv->bus->p);
        if ((drv->bus->probe && drv->probe) ||
         (drv->bus->remove && drv->remove) ||
         (drv->bus->shutdown && drv->shutdown))
            printk(KERN_WARNING "Driver '%s' needs updating - please use "
                "bus_type methods\n", drv->name);
        other = driver_find(drv->name, drv->bus);
        if (other) {
            put_driver(other);
            printk(KERN_ERR "Error: Driver '%s' is already registered, "
                "aborting...\n", drv->name);
            return -EBUSY;
        }
        ret = bus_add_driver(drv);    //把driver添加到bus去。
        if (ret)
            return ret;
        ret = driver_add_groups(drv, drv->groups);    //加进组里
        if (ret)
            bus_remove_driver(drv);
        return ret;
    }
    EXPORT_SYMBOL_GPL(driver_register);
    /**
     * driver_unregister - remove driver from system.
     * @drv: driver.
     *
     * Again, we pass off most of the work to the bus-level call.
     */
    void driver_unregister(struct device_driver *drv)
    {
        if (!drv || !drv->p) {
            WARN(1, "Unexpected driver unregister!\n");
            return;
        }
        driver_remove_groups(drv, drv->groups);
        bus_remove_driver(drv);
    }
    EXPORT_SYMBOL_GPL(driver_unregister);

3. 驱动程序的属性结构，driver_attribute:

    struct driver_attribute {
        struct attribute attr;
        ssize_t (*show)(struct device_driver *driver, char *buf);
        ssize_t (*store)(struct device_driver *driver, const char *buf,
                 size_t count);
    };

a. 可用 DRIVER_ATTR 宏声明：

    #define DRIVER_ATTR(_name, _mode, _show, _store)    \
    struct driver_attribute driver_attr_##_name =        \
        __ATTR(_name, _mode, _show, _store)

b.也可用下面函数创建属性文件：

    /**
     * driver_create_file - create sysfs file for driver.
     * @drv: driver.
     * @attr: driver attribute descriptor.
     */
    int driver_create_file(struct device_driver *drv,
             const struct driver_attribute *attr)
    {
        int error;
        if (drv)
            error = sysfs_create_file(&drv->p->kobj, &attr->attr);
        else
            error = -EINVAL;
        return error;
    }
    EXPORT_SYMBOL_GPL(driver_create_file);
    /**
     * driver_remove_file - remove sysfs file for driver.
     * @drv: driver.
     * @attr: driver attribute descriptor.
     */
    void driver_remove_file(struct device_driver *drv,
                const struct driver_attribute *attr)
    {
        if (drv)
            sysfs_remove_file(&drv->p->kobj, &attr->attr);
    }
    EXPORT_SYMBOL_GPL(driver_remove_file);