query regarding I2C controller on MPC8260

query regarding I2C controller on MPC8260

[Vijay Padiyar]

Hi there

I am using an MPC8260-based target board. My target is running U-Boot 1.1.2
as the bootloader and Linux-2.6.10 as the kernel with BusyBox-1.0. I wish to
use the I2C controller on the MPC8260 to access an external EEPROM connected
to it. I need to do this from *user space*.

>From what I understand, we can open the I2C device with the open command
from our application as follows:

ret = open ("/dev/i2c-0", O_RDWR);

After this, the device should be accessible using either standard I2C
functions or SMBus functions.

I read that if the I2C controller supports SMBus, it will be preferable to
access the device via the SMBus read/write functions, as they seem to be
more "efficient." What I want to know is, does the PowerPC I2C controller
support the SMBus protocol? I don't think it does, judging from the MPC8260
manual, but just want to be sure.

Also, do we need to create the /dev/i2c-0 device file manually or will it be
created on the fly?

Regards

Vijay Padiyar

http://www.vijaypadiyar.eu.tf

Re: query regarding I2C controller on MPC8260

[Yuli Barcohen]

>>>>> Vijay Padiyar writes:

    Vijay> Hi there I am using an MPC8260-based target board. My target
    Vijay> is running U-Boot 1.1.2 as the bootloader and Linux-2.6.10 as
    Vijay> the kernel with BusyBox-1.0. I wish to use the I2C controller
    Vijay> on the MPC8260 to access an external EEPROM connected to
    Vijay> it. I need to do this from *user space*.

    Vijay> From what I understand, we can open the I2C device with the
    Vijay> open command from our application as follows:

    Vijay> ret = open ("/dev/i2c-0", O_RDWR);

    Vijay> After this, the device should be accessible using either
    Vijay> standard I2C functions or SMBus functions.

    Vijay> I read that if the I2C controller supports SMBus, it will be
    Vijay> preferable to access the device via the SMBus read/write
    Vijay> functions, as they seem to be more "efficient." What I want
    Vijay> to know is, does the PowerPC I2C controller support the SMBus
    Vijay> protocol? I don't think it does, judging from the MPC8260
    Vijay> manual, but just want to be sure.

It does not support SMBus but since it's a full-featured I2C controller,
it's not a problem. SMBus emulation mode can be used on any I2C
controller.

    Vijay> Also, do we need to create the /dev/i2c-0 device file
    Vijay> manually or will it be created on the fly?

It depends on the /dev filesystem which you use. If it's devfs (or you
use udev), the file will be created on the fly, otherwise you have to
create it manually.

-- 
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 Yuli Barcohen       | Phone +972-9-765-1788 |  Software Project Leader
 yuli@arabellasw.com | Fax   +972-9-765-7494 | Arabella Software, Israel
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