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

From: Ray Jui
Date: Fri Aug 30 2019 - 14:35:16 EST

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,