linux I2C 驱动之----i2c驱动的注册过程

armeasy

Linux下i2c驱动的加载过程，分为i2c设备层、i2c adapter层与i2c核心层
i2c设备驱动层也就是我们为特定i2c设备编写的驱动，下面是我自己理解的i2c驱动的注册过程

在我们写的i2c设备驱动中，我们会调用i2c_add_driver()开始i2c设备驱动的注册，该函数调用
i2c_register_driver完成所有注册操作
static inline int i2c_add_driver(struct i2c_driver *driver)
{

return i2c_register_driver(THIS_MODULE, driver);

}

i2c_register_driver会调用driver_register() 来将设备驱动添加到总线的设备驱动链表中：

int i2c_register_driver(struct module *owner, struct i2c_driver *driver)

{

int res;

/* Can't register until after driver model init */

if (unlikely(WARN_ON(!i2c_bus_type.p)))

return -EAGAIN;

driver->driver.owner = owner;

driver->driver.bus = &i2c_bus_type;

/* When registration returns, the driver core

* will have called probe() for all matching-but-unbound devices.

*/

res = driver_register(&driver->driver);

if (res)

return res;

pr_debug("i2c-core: driver [%s] registered\n", driver->driver.name);

INIT_LIST_HEAD(&driver->clients);

/* Walk the adapters that are already present */

mutex_lock(&core_lock);

bus_for_each_dev(&i2c_bus_type, NULL, driver, __attach_adapter);

mutex_unlock(&core_lock);

return 0;

}

在driver_register中，通过driver_find来判断驱动是否已经注册，然后会调用

bus_add_drive

将设备驱动添加到总线上

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);

if (ret)

return ret;

ret = driver_add_groups(drv, drv->groups);

if (ret)

bus_remove_driver(drv);

return ret;

}

在bus_add_driver中初始化priv->klist_devices的值，并将priv赋值给drv->p

**************************************************************************

1、在arch/arm/mach-xxx/ 自己的平台文件里添加i2c信息，美其名曰：i2c_board_info

例如：

static struct i2c_board_info __initdata xxxi2c_board_info[] = {
    {
        I2C_BOARD_INFO("abcd1", 0x20), /* 字符串要与后面的匹配，0x20是从设备地址 */
        .platform_data = 0,
    },
    {
        I2C_BOARD_INFO("abcd2", 0x21),
        .platform_data = 0,
    },
};

然后调用i2c_register_board_info(1, xxxi2c_board_info, ARRAY_SIZE(xxxi2c_board_info));

第一个参数是0还是1，我还不知道:-(

2、在另外一个设备驱动文件里，比如你放到/driver/char下做字符设备，一般是module_init(func_init())形式，则调用i2c_add_driver()即可，有几个要定义：

static const struct i2c_device_id xxx_led_id[] = {
    { "abcd1", 0 }, /* 该名称必须与BOARD_INFO的匹配才会调用probe函数 */
    { "abcd2", 0 },
    { }
};
MODULE_DEVICE_TABLE(i2c, xxx_led_id);

static struct i2c_driver xxx_led_driver = {
    .driver        = {
        .name    = "yourname", /* 该名字不需要与别的匹配 */
        .owner  = THIS_MODULE,
    },
    .probe        = xxx_led_probe,
    .remove        = xxx_remove,
    .id_table    = xxx_led_id,
};

看到了吧，struct i2c_device_id里面的字符串与 I2C_BOARD_INFO里面的匹配后，xxx_led_probe才会调用。

如果不想用同一个probe，那就在写一个struct i2c_device_id和struct i2c_driver