Re: [PATCH v1 1/1] i2c: iproc: Add i2c repeated start capability

Ray Jui <ray.jui@xxxxxxxxxxxx> · Tue, 3 Sep 2019 16:11:16 -0700

On 8/31/19 2:49 AM, Wolfram Sang wrote:
Hi Ray,

With all the limitations in place, I wonder if it might be easier to
implement an smbus_xfer callback instead? What is left that makes this
controller more than SMBus and real I2C?

Right. But what is the implication of using smbus_xfer instead of
master_xfer in our driver?

Does it mean it will break existing functions of the i2c app that our
customers developed based on i2cdev (e.g., I2C_RDWR)?

If the customers uses I2C_RDWR (and it cannot be mapped to i2c_smbus_*
calls) then this is an indication that there is some I2C functionality
left which the HW can provide. I'd be interested which one, though.

1) Does

Maybe you wanted to describe it here and it got accidently cut off? >

I think you are right that the controller does not seem to support 
additional I2C features in addition to SMBUS.

However, my concern of switching to the smbus_xfer API is:

1) Some customers might have used I2C_RDWR based API from i2cdev. 
Changing from master_xfer to smbus_xfer may break the existing 
applications that are already developed.

2) The sound subsystem I2C regmap based implementation seems to be using 
i2c_ based API instead of smbus_ based API. Does this mean this will 
also break most of the audio codec drivers with I2C regmap API based usage?

Thanks,

Ray

Regards,

    Wolfram