Linux: Instantiate from user-space : eeprom new_device

问题

Environment : x86 / Ubuntu 14.04

I want obtain something similar to

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

But because in x86 no Device Tree is available, I am follow i2c/instantiating-device document in the Linux kernel and use "Method 4: Instantiate from user-space".

Process to instantiate:

Load at24 driver
Load i2c-dev driver

Instantiate:

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

Response from kernel in dmesg:

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

A directory is created "0-0050". Found in /sys/bus/i2c/devices/i2c-0/0-0050
This directory contains several files, but there is no file called "eeprom" in it.

Why the "eeprom" files are not created?

P.S:

The directory contains:

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

And file "name" contains:

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

回答1:

Use "24c32" instead of "eeprom" when instantiate I2C devices.

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

In my board with AT24C02 SPD EEPROM, instantiate AT24C02 on bus 2

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

The kernel message shows

[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

The directory contains

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

The eeprom file is

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

来源：https://stackoverflow.com/questions/52499762/linux-instantiate-from-user-space-eeprom-new-device

标签

Linux

linux-kernel

kernel-module

i2c

eeprom