kernel and i2c write command

Hi Daniel,

I will forward this to the Linux experts.

Hi Daniel,

The first parameter of i2c_master_send() function is basically just a handle to the slave device, pointer to i2c_client structure.

Detailed explanation of i2c_client structure can be found in include/linux/i2c.h file (bellow explanation is taken from sources for AM57xx, but this is a general rule and should be very similar in the AM335x sources):

 * struct i2c_client - represent an I2C slave device
 * @flags: I2C_CLIENT_TEN indicates the device uses a ten bit chip address;
 *    I2C_CLIENT_PEC indicates it uses SMBus Packet Error Checking
 * @addr: Address used on the I2C bus connected to the parent adapter.
 * @name: Indicates the type of the device, usually a chip name that's
 *    generic enough to hide second-sourcing and compatible revisions.
 * @adapter: manages the bus segment hosting this I2C device
 * @driver: device's driver, hence pointer to access routines
 * @dev: Driver model device node for the slave.
 * @irq: indicates the IRQ generated by this device (if any)
 * @detected: member of an i2c_driver.clients list or i2c-core's
 *    userspace_devices list
 *
 * An i2c_client identifies a single device (i.e. chip) connected to an
 * i2c bus. The behaviour exposed to Linux is defined by the driver
 * managing the device.

The structure should be populated upon registering of the I2C functionality of the slave device.

Hope this helps you.

Best Regards,

Yordan

Ok Yordan, I see this information, but that is not enough. I tried many ways to write in i2c. To use the drive, I need the correct client struct memory pointer. As you can see it is necessary in functions like: 

  int ret = i2c_master_send( &client, value, 4);

or 

s32 i2c_smbus_write_byte(const struct i2c_client *client, u8 value)

I tried unsuccesfull recover client pointer with the bellow code:

adapter = i2c_get_adapter(i2c_instance); // in my case i2c_instance could be 1, 2, or 3.
client.adapter = adapter;
client.addr = 0x70;  // the bus adress of my component linked to i2c-2
client.flags = I2C_M_TEN;

I attached the file board-am335xevm.c  that has backlinght_on function were is the above code. In the same file is the definition of the component attached to i2c-2. It works very well in linux user space, but in kernel space I can't communicate with it.

check by:

static struct i2c_board_info am335x_i2c2_boardinfo[]

I tried to write in u-boot, even with no success. At board.c file:

//df db
{
   udelay(9999999);
   uchar data[] = { 0xFF, 0XFF, 0XCF, 0X00};
   int ret = i2c_write(0X70, 0, 0, data, 4); /// it was tried bus 0,1,2 and 3.
   if( ret!=0 )
        puts("\n\n ---------------------> ERROR \n\n");
   else
        puts("\n\n ---------------------> DISPLAY OK\n\n");
}

Is in u-boot possible to write in i2c different of 0? attached are board.c and mux.c of u-boot

do you have an alternative?

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