/sys/bus/i2c/devices下的内容与i2c_board_info结构体

在目录/sys/bus/i2c/devices下能发现系统中的I2C设备，如下：

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1. # ls 
2. 0-0034 
3. 0-0030 
4. 0-0011 
5. 0-0058 

# ls 0-0034 0-0030 0-0011 0-0058

这些设备就是系统中存在的设备。

这些设备是怎么来的？

在你对应的machine配置里会执行“i2c_register_board_info”一个函数，它会将一个i2c_board_info的结构体注册进系统，

这个i2c_board_info的结构体里就描述了板载的所有I2C设备信息，如下例：

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1. static struct i2c_board_info littleton_i2c_board_info[] = { 
2. #if defined(CONFIG_PXA3xx_MICCO) || defined(CONFIG_PXA3xx_MICCO_MODULE) 
3.     { 
4.         .type   = "micco", 
5.         .addr       = 0x34, 
6.         .platform_data  = &micco_data, 
7.         .irq        = IRQ_GPIO(mfp_to_gpio(MFP_PIN_GPIO18)), 
8.     }, 
9. #endif 
10. #if defined(CONFIG_GPIO_MAX7320) || defined(CONFIG_GPIO_MAX7320_MODULE) 
11.     { 
12.         .type   = "max7320", 
13.         .addr       = 0x50, 
14.         .platform_data  = &exp0_pdata, 
15.     }, 
16. #endif 
17. #if defined(CONFIG_GPIO_MAX7321) || defined(CONFIG_GPIO_MAX7321_MODULE) 
18.     { 
19.         /* on 8385 WLAN Board */ 
20.         .type   = "max7321", 
21.         .addr       = 0x60, 
22.         .platform_data  = &exp1_pdata[BOARD_8385_WLAN], 
23.     }, 
24.     { 
25.         /* on UMTS Board */ 
26.         .type   = "max7321", 
27.         .addr       = 0x61, 
28.         .platform_data  = &exp1_pdata[BOARD_UMTS], 
29.     }, 
30.     { 
31.         /* on Siemens Baseband Radio Interposer Board */ 
32.         .type   = "max7321", 
33.         .addr       = 0x62, 
34.         .platform_data  = &exp1_pdata[BOARD_SIEMENS_BASEBAND], 
35.     }, 
36.     { 
37.         /* on 8688 WLAN/Camera Board */ 
38.         .type   = "max7321", 
39.         .addr       = 0x63, 
40.         .platform_data  = &exp1_pdata[BOARD_8688_WLAN_CAMERA], 
41.     }, 
42.     { 
43.         /* on Camera Board */ 
44.         .type   = "max7321", 
45.         .addr       = 0x64, 
46.         .platform_data  = &exp1_pdata[BOARD_CAMERA], 
47.     }, 
48.     { 
49.         /* on 8686 WLAN/Camera Board */ 
50.         .type   = "max7321", 
51.         .addr       = 0x66, 
52.         .platform_data  = &exp1_pdata[BOARD_8386_WLAN_CAMERA], 
53.     }, 
54.     { 
55.         /* on 8385 WLAN/Camera Board */ 
56.         .type   = "max7321", 
57.         .addr       = 0x6c, 
58.         .platform_data  = &exp1_pdata[BOARD_8385_WLAN_CAMERA], 
59.     }, 
60.     { 
61.         /* on 8688 WLAN Board */ 
62.         .type   = "max7321", 
63.         .addr       = 0x6d, 
64.         .platform_data  = &exp1_pdata[BOARD_8688_WLAN], 
65.         .irq        = IRQ_GPIO(mfp_to_gpio(MFP_PIN_GPIO77)), 
66.     }, 
67. #endif 
68. #if defined(CONFIG_PXA_CAMERA) 
69.     { 
70.         .type   = "sensor_ov7673", 
71.         .addr       = 0x21, 
72.         .platform_data  = &ov7673_sensor_data, 
73.     }, 
74.     {    
75.         .type   = "sensor_ov5623", 
76.         .addr       = 0x30, 
77.         .platform_data  = &ov5623_sensor_data, 
78.     }, 
79. #endif 
80. }; 

static struct i2c_board_info littleton_i2c_board_info[] = { #if defined(CONFIG_PXA3xx_MICCO) || defined(CONFIG_PXA3xx_MICCO_MODULE) { .type = "micco", .addr = 0x34, .platform_data = &micco_data, .irq = IRQ_GPIO(mfp_to_gpio(MFP_PIN_GPIO18)), }, #endif #if defined(CONFIG_GPIO_MAX7320) || defined(CONFIG_GPIO_MAX7320_MODULE) { .type = "max7320", .addr = 0x50, .platform_data = &exp0_pdata, }, #endif #if defined(CONFIG_GPIO_MAX7321) || defined(CONFIG_GPIO_MAX7321_MODULE) { /* on 8385 WLAN Board */ .type = "max7321", .addr = 0x60, .platform_data = &exp1_pdata[BOARD_8385_WLAN], }, { /* on UMTS Board */ .type = "max7321", .addr = 0x61, .platform_data = &exp1_pdata[BOARD_UMTS], }, { /* on Siemens Baseband Radio Interposer Board */ .type = "max7321", .addr = 0x62, .platform_data = &exp1_pdata[BOARD_SIEMENS_BASEBAND], }, { /* on 8688 WLAN/Camera Board */ .type = "max7321", .addr = 0x63, .platform_data = &exp1_pdata[BOARD_8688_WLAN_CAMERA], }, { /* on Camera Board */ .type = "max7321", .addr = 0x64, .platform_data = &exp1_pdata[BOARD_CAMERA], }, { /* on 8686 WLAN/Camera Board */ .type = "max7321", .addr = 0x66, .platform_data = &exp1_pdata[BOARD_8386_WLAN_CAMERA], }, { /* on 8385 WLAN/Camera Board */ .type = "max7321", .addr = 0x6c, .platform_data = &exp1_pdata[BOARD_8385_WLAN_CAMERA], }, { /* on 8688 WLAN Board */ .type = "max7321", .addr = 0x6d, .platform_data = &exp1_pdata[BOARD_8688_WLAN], .irq = IRQ_GPIO(mfp_to_gpio(MFP_PIN_GPIO77)), }, #endif #if defined(CONFIG_PXA_CAMERA) { .type = "sensor_ov7673", .addr = 0x21, .platform_data = &ov7673_sensor_data, }, { .type = "sensor_ov5623", .addr = 0x30, .platform_data = &ov5623_sensor_data, }, #endif };

可以发现，在目录/sys/bus/i2c/devices下的设备就是这个i2c_board_info结构体里所描述的I2C设备，

而/sys/bus/i2c/devices下的设备名字就是根据i2c_board_info结构体中定义的I2C Address来命名的。

所以添加一个I2C设备时，除了需要编写这个I2C设备的驱动之外，还需要在machine里面加入I2C设备的i2c_board_info内容。