Re: [RFC PATCH 0/4] hw/i2c: i2c slave mode support

[Damien Hedde <damien.hedde@greensocs.com>]

On 4/1/22 08:29, Klaus Jensen wrote:
> On Mar 31 15:32, Corey Minyard wrote:
>> On Thu, Mar 31, 2022 at 06:57:33PM +0200, Klaus Jensen wrote:
>>> From: Klaus Jensen <k.jensen@samsung.com>
>>>
>>> Hi all,
>>>
>>> This RFC series adds I2C "slave mode" support for the Aspeed I2C
>>> controller as well as the necessary infrastructure in the i2c core to
>>> support this.
>>
>> I've been wondering when this would happen :).  I had put some thought
>> into how this would work, but hadn't come up with anything good.
>>
>> The big disadvantage of this is you are adding an interface that is
>> incompatible with the current masters and slaves.  So you are using the
>> same I2C bus, but slaves written this way cannot talk to existing
>> masters, and masters written this way cannot talk to existing slave.
>> You could adapt the masters to be able to work either way, and I suppose
>> some slaves that could do it could have both an async send and a normal
>> send.
> 
> Would it make sense to introduce a QOM Interface to differentiate
> between the slave/master types?
> 

Probably.

I expect a normal slave-only I2C device will be compatible with any 
master (having or having not this feature) in real life ?

It would be great if the compatibility between "a I2C slave requiring 
the slave-mode from the bus" and the bus could be checked during the 
device plug.

--
Damien