如何在kernel空间中使用i2c驱动

Question

I have wrote a character driver to control my embedded hardware with my application, In my driver there is a feature to send a command to an I2C device which is connected to my embedded device.

in command line I am able to send the following code to my device:

i2cset  -y 0 0x2c 0x00 0x05

I want to do same thing in kernel space within my driver, but I did not find a sample, all I got was in userspace, how can I do that in kernel space?

edit:

I know that with " i2c_master_send " or " i2c_smbus_read_byte " function I can send data to i2c devices, bu this function gets a structure called " i2c_client ", I don't know how should I suppose to fill this structure to send data. It might be really silly but I could not figure it out how can I fill this structure.

Answer 1

I have reached my goal with following code in my driver:

****Please read my edit before using this code*****

#define VOL1_CHIP_ADDRESS 0x2c
#define VOL1_DATA_ADDRESS 0

struct i2c_client *clientstr;
struct file * fp;

...

mm_segment_t oldfs;

oldfs = get_fs();
set_fs(KERNEL_DS);
fp = filp_open("/dev/i2c-0",O_RDWR,0);
clientstr = (struct i2c_client *)fp->private_data;
clientstr->addr=VOL1_CHIP_ADDRESS;
i2c_smbus_write_byte_data(clientstr,VOL1_DATA_ADDRESS,0x05);
filp_close(fp,NULL);
set_fs(oldfs);

EDIT:

So I did what I wanted in kernel, opening a file in kernel space regardless of any suggestions not to do so.

But I needed to open a file in kernel module...

So why every body said don't open user space files in kernel? In these two articles there are some reasons to not using files in kernel, this link and this link .

there are some reasons like: 1- kernel module may lose CPU at any time and the file which is opened by kernel may close.

2- I am not sure really about this, But they said files needs to have a process to stay opened but kernel module itself is not a process(maybe I am wrong.).

3- If any error happens while working with files(open/close/read/write), kernel module can not handle it and causes kernel panic...

I have experienced a lot of kernel panics only while opening and closing the file I wanted to work with. These are some of reasons why you should not use files in kernel modules, So as every body said before "If you need to use files in kernel module you probably did something wrong in your code!"