linux I2C 驅動之----i2c驅動的註冊過程(i2c_register_driver->driver_register(&driver->driver)->driver_find)
Linux下i2c驅動的載入過程，分為i2c裝置層、i2c adapter層與i2c核心層
i2c裝置驅動層也就是我們為特定i2c裝置編寫的驅動，下面是我自己理解的i2c驅動的註冊過程
在我們寫的i2c裝置驅動中，我們會呼叫i2c_add_driver()開始i2c裝置驅動的註冊，該函式呼叫
i2c_register_driver完成所有註冊操作
static inline int i2c_add_driver(struct i2c_driver *driver)
{
return i2c_register_driver(THIS_MODULE, driver);
}
i2c_register_driver會呼叫driver_register() 來將裝置驅動新增到匯流排的裝置驅動連結串列中：
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，通過driver_find來判斷驅動是否已經註冊，然後會呼叫
bus_add_drive
將裝置驅動新增到總線上
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，並將priv賦值給drv->p
**************************************************************************
1、在arch/arm/mach-xxx/ 自己的平臺檔案裡新增i2c資訊，美其名曰：i2c_board_info
例如：
static struct i2c_board_info __initdata xxxi2c_board_info[] = { { I2C_BOARD_INFO("abcd1", 0x20), /* 字串要與後面的匹配，0x20是從裝置地址 */ .platform_data = 0, }, { I2C_BOARD_INFO("abcd2", 0x21), .platform_data = 0, }, };
然後呼叫i2c_register_board_info(1, xxxi2c_board_info, ARRAY_SIZE(xxxi2c_board_info));
第一個引數是0還是1，我還不知道:-(
2、在另外一個裝置驅動檔案裡，比如你放到/driver/char下做字元裝置，一般是module_init(func_init())形式，則呼叫i2c_add_driver()即可，有幾個要定義：
static const struct i2c_device_id xxx_led_id[] = { { "abcd1", 0 }, /* 該名稱必須與BOARD_INFO的匹配才會呼叫probe函式 */ { "abcd2", 0 }, { } }; MODULE_DEVICE_TABLE(i2c, xxx_led_id); static struct i2c_driver xxx_led_driver = { .driver = { .name = "yourname", /* 該名字不需要與別的匹配 */ .owner = THIS_MODULE, }, .probe = xxx_led_probe, .remove = xxx_remove, .id_table = xxx_led_id, };
看到了吧，struct i2c_device_id裡面的字串與 I2C_BOARD_INFO裡面的匹配後，xxx_led_probe才會呼叫。
如果不想用同一個probe，那就在寫一個struct i2c_device_id和struct i2c_driver