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

[Ray Jui]

On 8/30/19 5:56 AM, Wolfram Sang wrote:
> Hi everyone,
>
> > +/*
> > + * If 'process_call' is true, then this is a multi-msg transfer that requires
> > + * a repeated start between the messages.
> > + * More specifically, it must be a write (reg) followed by a read (data).
> > + * The i2c quirks are set to enforce this rule.
> > + */
>
> 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)?

1) Does
> > +	/* Process the read message if this is process call */
>
> Also, the term "process call" here seriously sounds like SMBus.
>
> > +		addr = msg->addr << 1 | 1;
>
> addr = i2c_8bit_addr_from_msg(msg);
>
> > +		u32 protocol;
>
> Hmm, another SMBus terminology.
>
>
> > +	if (num > 2) {
> > +		dev_err(iproc_i2c->device,
> > +			"Only support up to 2 messages. Current msg count %d\n",
> > +			num);
> > +		return -EOPNOTSUPP;
> > +	}
>
> With your quirks flags set, the core checks it for you.
>
> Kind regards,
>
>     Wolfram