MX6 i2C linux driver

[karstenklein]

Hi all,

I currently work with the MCIMMX6Q-SDB board from Freescale. The kernel is taken from Yocto/Dylan core-image-base as it is, without change in config.

I tried to write a small userspace-application which uses the accelerator MMA8451 via I2C.

I figured out how the MMA is connected to the CPU and tried to do the following:

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

    if (dev < 0) {

	err = errno;
	perror("==> ERROR  open:");
	printf("errno = %d\n", err);
	close(dev);
	exit (1);

    }

    if (ioctl(dev, I2C_SLAVE, I2C_DEV_ADR_MMA8451) < 0) {

	err = errno;
	perror("==> Error ioctl:");
	printf("errno = %d\n", err);
	close(dev);
	exit (1);

    }

The syscall ioclt comes up with the following error;

==> Error ioctl:: Device or resource busy

errno = 16

If I use

if (ioctl(dev, I2C_SLAVE_FORCE, I2C_DEV_ADR_MMA8451) < 0) {

instead, the I2C basicly works.

After some search, I found the following:

root@imx6qsabresd:/sys/devices/virtual/input/input3# cat name

mma845x

So this makes me thinking, that there is a virtual device driver in the system which uses the i2c-driver as well.

But I cant find any informations about this.

Does anyone have experience on that ?

Best regards

Karsten

[YixingKong]

Klein

This discussion is closed since no activity. If you still need help, please feel free to reply with an update to this discussion, or create another discussion.

Thanks,

Yixing

[YixingKong]

Klein

Had your issue got resolved? If yes, we are going to close the discussion in 3 days. If you still need help, please feel

free to reply with an update to this discussion.

Thanks,
Yixing

[raymondwang]

If your register i2c device with same address in board init,userland /dev/i2c-x access will report device busy.

See details in drivers/i2c/i2c-dev.c

/* NOTE:  devices set up to work with "new style" drivers

  * can't use I2C_SLAVE, even when the device node is not

  * bound to a driver.  Only I2C_SLAVE_FORCE will work.

  *

  * Setting the PEC flag here won't affect kernel drivers,

  * which will be using the i2c_client node registered with

  * the driver model core.  Likewise, when that client has

  * the PEC flag already set, the i2c-dev driver won't see

  * (or use) this setting.

  */

  if ((arg > 0x3ff) ||

     (((client->flags & I2C_M_TEN) == 0) && arg > 0x7f))

  return -EINVAL;

  if (cmd == I2C_SLAVE && i2cdev_check_addr(client->adapter, arg))

  return -EBUSY;

  /* REVISIT: address could become busy later */

  client->addr = arg;