Linux:从用户空间实例化:eeprom new_device

Question

环境:x86/Ubuntu 14.04

我想获得类似于

的东西

&i2c0 { 
    eeprom: eeprom@50 { 
        compatible = "at,24c32"; 
        reg = <0x50>; 
    }; 
};

但因为在 x86 中没有可用的设备树，我按照 Linux 内核中的 i2c/instantiating-device 文档并使用“方法 4:从用户空间实例化”。

实例化过程:

• 加载24位驱动
• 加载 i2c-dev 驱动

• 实例化:

  # echo eeprom 0x50 > /sys/bus/i2c/devices/i2c-0/new_device
  

• dmesg 中内核的响应:

  i2c i2c-0: new_device: Instantiated device eeprom at 0x50
  

• 创建目录“0-0050”。位于 /sys/bus/i2c/devices/i2c-0/0-0050

• 此目录包含多个文件，但其中没有名为“eeprom”的文件。

为什么没有创建“eeprom”文件？

附言:

目录包含:

root@peio-t52r:~/etxoh# ls -la /sys/bus/i2c/devices/i2c-0/0-0050
total 0
drwxr-xr-x 3 root root    0 sep 25 15:06 .
drwxr-xr-x 5 root root    0 sep 25 14:48 ..
-r--r--r-- 1 root root 4096 sep 25 15:06 modalias
-r--r--r-- 1 root root 4096 sep 25 15:06 name
drwxr-xr-x 2 root root    0 sep 25 15:06 power
lrwxrwxrwx 1 root root    0 sep 25 15:06 subsystem -> ../../../../../bus/i2c
-rw-r--r-- 1 root root 4096 sep 25 15:06 uevent

文件“名称”包含:

root@peio-t52r:~/etxoh# cat /sys/bus/i2c/devices/i2c-0/0-0050/name
eeprom

Answer 1

实例化 I2C 设备时使用“24c32”而不是“eeprom”。

# echo 24c32 0x50 > /sys/bus/i2c/devices/i2c-0/new_device

在我的带有 AT24C02 SPD EEPROM 的开发板中，在总线 2 上实例化 AT24C02

# echo 24c02 0x50 > /sys/class/i2c-adapter/i2c-2/new_device

内核消息显示

[21230.868376] at24 2-0050: 256 byte 24c02 EEPROM, writable, 1 bytes/write
[21230.868423] i2c i2c-2: new_device: Instantiated device 24c02 at 0x50

目录包含

root@:/sys/bus/i2c/devices/i2c-2/2-0050# ls
2-00500/  driver@  eeprom  modalias  name  power/  subsystem@  uevent

eeprom文件是

root@:/sys/bus/i2c/devices/i2c-2/2-0052# hexdump -C eeprom 
00000000  23 11 0c 03 45 21 00 08  00 60 00 03 02 03 00 00  |#...E!...`......|
00000010  00 00 07 0d f8 0f 00 00  6e 6e 6e 11 00 6e f0 0a  |........nnn..n..|
00000020  20 08 00 05 00 f0 2b 34  28 00 78 00 14 3c 00 00  | .....+4(.x..<..|
00000030  00 00 00 00 00 00 00 00  00 00 00 00 16 36 0b 35  |.............6.5|
00000040  16 36 0b 35 00 00 16 36  0b 35 16 36 0b 35 00 00  |.6.5...6.5.6.5..|
00000050  00 00 00 00 00 00 00 00  00 00 00 00 00 00 00 00  |................|
*
00000070  00 00 00 00 00 00 9c b5  00 00 00 00 e7 d6 0b e3  |................|
00000080  0f 11 02 00 00 00 00 00  00 00 00 00 00 00 00 00  |................|
00000090  00 00 00 00 00 00 00 00  00 00 00 00 00 00 00 00  |................|
*
000000f0  00 00 00 00 00 00 00 00  00 00 00 00 00 00 db 08  |................|
00000100