3.4.2內核下的I2C驅動框架解析

第一種方法：

at24cxx_drv.c源碼：

#include "linux/kernel.h"

#include "linux/module.h"

#include "linux/platform_device.h"

#include "linux/i2c.h"

#include "linux/err.h"

#include "linux/regmap.h"

#include "linux/slab.h"

static int __devinit at24cxx_probe(struct i2c_client *client,

const struct i2c_device_id *id)

{

printk("%s %s %dn", __FILE__, __FUNCTION__, __LINE__);

return 0;

}

static int __devexit at24cxx_remove(struct i2c_client *client)

{

printk("%s %s %dn", __FILE__, __FUNCTION__, __LINE__);

return 0;

}

static const struct i2c_device_id at24cxx_id_table[] = {

{ "at24c08", 0 },

{}

};

// 1. 分配/設置i2c_driver //

static struct i2c_driver at24cxx_driver = {

.driver = {

.name = "100ask",

.owner = THIS_MODULE,

},

.probe = at24cxx_probe,

.remove = __devexit_p(at24cxx_remove),

.id_table = at24cxx_id_table,

};

static int at24cxx_drv_init(void)

{

// 2. 注冊i2c_driver //

i2c_add_driver(&at24cxx_driver);

return 0;

}

static void at24cxx_drv_exit(void)

{

i2c_del_driver(&at24cxx_driver);

}

module_init(at24cxx_drv_init);

module_exit(at24cxx_drv_exit);

MODULE_LICENSE("GPL");

at24cxx_dev.c源碼：

#include "linux/kernel.h"

#include "linux/module.h"

#include "linux/platform_device.h"

#include "linux/i2c.h"

#include "linux/err.h"

#include "linux/regmap.h"

#include "linux/slab.h"

static struct i2c_board_info at24cxx_info = {

I2C_BOARD_INFO("at24c08", 0x50),

};

static struct i2c_client *at24cxx_client;

static int at24cxx_dev_init(void)

{

struct i2c_adapter *i2c_adap;

i2c_adap = i2c_get_adapter(0);

at24cxx_client = i2c_new_device(i2c_adap, &at24cxx_info);

i2c_put_adapter(i2c_adap);

return 0;

}

static void at24cxx_dev_exit(void)

{

i2c_unregister_device(at24cxx_client);

}

module_init(at24cxx_dev_init);

module_exit(at24cxx_dev_exit);

MODULE_LICENSE("GPL");

===============================================================

第二種方法：

at24cxx_drv.c源碼：

#include "linux/kernel.h"

#include "linux/module.h"

#include "linux/platform_device.h"

#include "linux/i2c.h"

#include "linux/err.h"

#include "linux/regmap.h"

#include "linux/slab.h"

static int __devinit at24cxx_probe(struct i2c_client *client,

const struct i2c_device_id *id)

{

printk("%s %s %dn", __FILE__, __FUNCTION__, __LINE__);

return 0;

}

static int __devexit at24cxx_remove(struct i2c_client *client)

{

printk("%s %s %dn", __FILE__, __FUNCTION__, __LINE__);

return 0;

}

static const struct i2c_device_id at24cxx_id_table[] = {

{ "at24c08", 0 },

{}

};

// 1. 分配/設置i2c_driver //

static struct i2c_driver at24cxx_driver = {

.driver = {

.name = "100ask",

.owner = THIS_MODULE,

},

.probe = at24cxx_probe,

.remove = __devexit_p(at24cxx_remove),

.id_table = at24cxx_id_table,

};

static int at24cxx_drv_init(void)

{

// 2. 注冊i2c_driver //

i2c_add_driver(&at24cxx_driver);

return 0;

}

static void at24cxx_drv_exit(void)

{

i2c_del_driver(&at24cxx_driver);

}

module_init(at24cxx_drv_init);

module_exit(at24cxx_drv_exit);

MODULE_LICENSE("GPL");

at24cxx_dev.c源碼：

#include "linux/kernel.h"

#include "linux/module.h"

#include "linux/platform_device.h"

#include "linux/i2c.h"

#include "linux/err.h"

#include "linux/regmap.h"

#include "linux/slab.h"

static struct i2c_client *at24cxx_client;

static const unsigned short addr_list[] = { 0x60, 0x50, I2C_CLIENT_END };

static int at24cxx_dev_init(void)

{

struct i2c_adapter *i2c_adap;

struct i2c_board_info at24cxx_info;

memset(&at24cxx_info, 0, sizeof(struct i2c_board_info));

strlcpy(at24cxx_info.type, "at24c08", I2C_NAME_SIZE);

i2c_adap = i2c_get_adapter(0);

at24cxx_client = i2c_new_probed_device(i2c_adap, &at24cxx_info, addr_list, NULL);

i2c_put_adapter(i2c_adap);

if (at24cxx_client)

return 0;

else

return -ENODEV;

}

static void at24cxx_dev_exit(void)

{

i2c_unregister_device(at24cxx_client);

}

module_init(at24cxx_dev_init);

module_exit(at24cxx_dev_exit);

MODULE_LICENSE("GPL");

=============================================================

第四種方法：

at24cxx_drv.c源碼：

#include "linux/kernel.h"

#include "linux/module.h"

#include "linux/platform_device.h"

#include "linux/i2c.h"

#include "linux/err.h"

#include "linux/regmap.h"

#include "linux/slab.h"

static int __devinit at24cxx_probe(struct i2c_client *client,

const struct i2c_device_id *id)

{

printk("%s %s %dn", __FILE__, __FUNCTION__, __LINE__);

return 0;

}

static int __devexit at24cxx_remove(struct i2c_client *client)

{

printk("%s %s %dn", __FILE__, __FUNCTION__, __LINE__);

return 0;

}

static const struct i2c_device_id at24cxx_id_table[] = {

{ "at24c08", 0 },

{}

};

static int at24cxx_detect(struct i2c_client *client,

struct i2c_board_info *info)

{

// 能運行到這里, 表示該addr的設備是存在的

* 但是有些設備單憑地址無法分辨(A芯片的地址是0x50, B芯片的地址也是0x50)

* 還需要進一步讀寫I2C設備來分辨是哪款芯片

* detect就是用來進一步分辨這個芯片是哪一款，并且設置info->type

//

printk("at24cxx_detect : addr = 0x%xn", client->addr);

// 進一步判斷是哪一款 //

strlcpy(info->type, "at24c08", I2C_NAME_SIZE);

return 0;

}

static const unsigned short addr_list[] = { 0x60, 0x50, I2C_CLIENT_END };

// 1. 分配/設置i2c_driver //

static struct i2c_driver at24cxx_driver = {

.class = I2C_CLASS_HWMON, // 表示去哪些適配器上找設備 //

.driver = {

.name = "100ask",

.owner = THIS_MODULE,

},

.probe = at24cxx_probe,

.remove = __devexit_p(at24cxx_remove),

.id_table = at24cxx_id_table,

.detect = at24cxx_detect, // 用這個函數來檢測設備確實存在 //

.address_list = addr_list, // 這些設備的地址 //

};

static int at24cxx_drv_init(void)

{

// 2. 注冊i2c_driver //

i2c_add_driver(&at24cxx_driver);

return 0;

}

static void at24cxx_drv_exit(void)

{

i2c_del_driver(&at24cxx_driver);

}

module_init(at24cxx_drv_init);

module_exit(at24cxx_drv_exit);

MODULE_LICENSE("GPL");

===============================================================

1. 框架

1.1 硬件協議簡介

1.2 驅動框架

1.3 bus-drv-dev模型及寫程序

a. 設備的4種構建方法(對于以下4種方法建議使用前3種，第四種方法迫不得已情況下使用)

a.1 定義一個i2c_board_info, 里面有:名字, 設備地址

然后i2c_register_board_info(busnum, ...) (把它們放入__i2c_board_list鏈表)

list_add_tail(&devinfo->list, &__i2c_board_list);

鏈表何時使用：

i2c_register_adapter > i2c_scan_static_board_info > i2c_new_device

使用限制：必須在 i2c_register_adapter 之前 i2c_register_board_info

所以：不適合我們動態加載insmod

a.2 直接i2c_new_device, i2c_new_probed_device

a.2.1 i2c_new_device : 認為設備肯定存在

a.2.2 i2c_new_probed_device ：對于"已經識別出來的設備"(probed_device)，才會創建("new")

i2c_new_probed_device

probe(adap, addr_list[i]) // 確定設備是否真實存在 //

info->addr = addr_list[i];

i2c_new_device(adap, info);

a.3 從用戶空間創建設備

創建設備

echo at24c08 0x50 > /sys/class/i2c-adapter/i2c-0/new_device

導致i2c_new_device被調用

刪除設備

echo 0x50 > /sys/class/i2c-adapter/i2c-0/delete_device

導致i2c_unregister_device

a.4 前面的3種方法都要事先確定適配器(I2C總線,I2C控制器)

如果我事先并不知道這個I2C設備在哪個適配器上，怎么辦？去class表示的所有的適配器上查找

有上一些I2C設備的地址是一樣，怎么繼續分配它是哪一款？用detect函數

static struct i2c_driver at24cxx_driver = {

.class = I2C_CLASS_HWMON, // 表示去哪些適配器上找設備 //

.driver = {

.name = "100ask",

.owner = THIS_MODULE,

},

.probe = at24cxx_probe,

.remove = __devexit_p(at24cxx_remove),

.id_table = at24cxx_id_table,

.detect = at24cxx_detect, // 用這個函數來檢測設備確實存在 //

.address_list = addr_list, // 這些設備的地址 //

};

去"class表示的這一類"I2C適配器，用"detect函數"來確定能否找到"address_list里的設備",

如果能找到就調用i2c_new_device來注冊i2c_client, 這會和i2c_driver的id_table比較，

如果匹配，調用probe

i2c_add_driver

i2c_register_driver

a. at24cxx_driver放入i2c_bus_type的drv鏈表

并且從dev鏈表里取出能匹配的i2c_client并調用probe

driver_register

b. 對于每一個適配器，調用__process_new_driver

對于每一個適配器，調用它的函數確定address_list里的設備是否存在

如果存在，再調用detect進一步確定、設置，然后i2c_new_device

// Walk the adapters that are already present //

i2c_for_each_dev(driver, __process_new_driver);

__process_new_driver

i2c_do_add_adapter

// Detect supported devices on that bus, and instantiate them //

i2c_detect(adap, driver);

for (i = 0; address_list[i] != I2C_CLIENT_END; i += 1) {

err = i2c_detect_address(temp_client, driver);

// 判斷這個設備是否存在：簡單的發出S信號確定有ACK //

if (!i2c_default_probe(adapter, addr))

return 0;

memset(&info, 0, sizeof(struct i2c_board_info));

info.addr = addr;

// 設置info.type

err = driver->detect(temp_client, &info);

i2c_new_device

b. 驅動的寫法

2. 完善設備驅動程序

3. 不自己寫驅動直接訪問

Device Drivers

I2C support

<*> I2C device interface

4. 編寫"總線(適配器adapter)"驅動

Device Drivers

I2C support

I2C Hardware Bus support

< > S3C2410 I2C Driver

nfs 30000000 192.168.1.123:/work/nfs_root/uImage_noi2cbus; bootm 30000000