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

[Ray Jui]

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