Re: [PATCH V7 3/6] i2c: qup: Transfer each i2c_msg in i2c_msgs without a stop bit

Wolfram Sang
2016-01-24T11:29:28Z

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Hi,

> "If this is the last message in a group, it is followed by a STOP.
> Otherwise it is followed by the next @i2c_msg transaction segment,
> beginning with a (repeated) START"

This is correct.

> So the expectation is that there is no 'STOP' bit inbetween individual
> i2c_msg segments with repeated 'START'. The QUP i2c hardware has no way
> to inform that there should not be a 'STOP' at the end of transaction.
> The only way to implement this is to coalesce all the i2c_msg in i2c_msgs
> in to one transaction and transfer them. Adding the support for the same.

So, there will not be a REP_START condition on the bus? I am sorry to
say that I can't accept this. A REP_START is a REP_START and nothing
else. There are devices which will get confused if there is no real
REP_START condition.

Without knowing the HW in detail, can't you implement I2C_M_NOSTART and
let the touchscreen driver use it via regmap? That would be the proper
way (from what I understand).

Regards,

Wolfram

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