DRIVER_ATTR and DEVICE_ATTR

最新推荐文章于 2023-06-12 11:08:47 发布

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本文介绍了Linux中设备属性和驱动程序属性的概念及其使用方法。通过DEVICE_ATTR和DRIVER_ATTR宏定义属性，并利用sysfs文件系统导出这些属性，使它们可以被应用程序读取和修改。

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Driver Attributes

~~~~~~~~~~~~~~~~~

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

Device drivers can export attributes via their sysfs directories.

Drivers can declare attributes using a DRIVER_ATTR macro that works

identically to the DEVICE_ATTR macro.

Example:

DRIVER_ATTR(debug,0644,show_debug,store_debug);

This is equivalent to declaring:

struct driver_attribute driver_attr_debug;

This can then be used to add and remove the attribute from the

driver's directory using:

int driver_create_file(struct device_driver *, const struct driver_attribute *);

void driver_remove_file(struct device_driver *, const struct driver_attribute *);

Device Attributes

~~~~~~~~~~~~~~~~~

struct device_attribute {
    struct attribute    attr;
    ssize_t (*show)(struct device *dev, struct device_attribute *attr,
            char *buf);
    ssize_t (*store)(struct device *dev, struct device_attribute *attr,
             const char *buf, size_t count);
};

Attributes of devices can be exported via drivers using a simple

procfs-like interface.

Please see Documentation/filesystems/sysfs.txt for more information

on how sysfs works.

Attributes are declared using a macro called DEVICE_ATTR:

#define DEVICE_ATTR(name,mode,show,store)

Example:

DEVICE_ATTR(power,0644,show_power,store_power);

This declares a structure of type struct device_attribute named

'dev_attr_power'. This can then be added and removed to the device's

directory using:

int device_create_file(struct device *device, struct device_attribute * entry);