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,我們會調用i2c_add_driver()開始i2c裝置驅動的註冊,該函數調用
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會調用driver_register() 來將裝置驅動添加到匯流排的裝置驅動鏈表中:
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,通過driver_find來判斷驅動是否已經註冊,然後會調用
bus_add_drive
將裝置驅動添加到匯流排上
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/ 自己的平台檔案裡添加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,
},
};
然後調用i2c_register_board_info(1, xxxi2c_board_info, ARRAY_SIZE(xxxi2c_board_info));
第一個參數是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,則調用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的匹配才會調用probe函數 */
{ "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才會調用。
如果不想用同一個probe,那就在寫一個struct i2c_device_id和struct i2c_driver