[virtio-comment] Re: [PATCH v2] virtio-i2c: add the device specification

[Jie Deng <jie.deng@intel.com>]

On 2020/10/26 9:22, Jie Deng wrote:

> On 2020/10/24 0:00, Michael S. Tsirkin wrote:
>
>> On Fri, Oct 23, 2020 at 02:51:25PM +0800, Jie Deng wrote:
>>> +
>>> +The driver queues requests to the virtqueues, and they are used by the
>>> +device. The request is the representation of one segment of an I2C
>>> +transaction. Each request is of form:
>>> +
>>> +\begin{lstlisting}
>>> +struct virtio_i2c_req {
>>> +        le16 addr;
>>> +        le16 flags;
>>> +        le16 len;
>>> +        u8 buf[];
>>> +        u8 status;
>>> +};
>>> +\end{lstlisting}
>>> +
>>> +The \field{addr} is the address of the I2C slave device.
>>> +
>>> +The first bit of \field{flags} indicates whether it is a read or 
>>> write request.
>>> +It means a read request if the first bit of \field{flags} is set, 
>>> otherwise
>>> +it is a write request. The rest bits of \field{flags} are reserved.
>>>
>>
>> So how does one creates a multi-segment transaction then?
>>
> The I2C doesn't support segments numbering and sorting.
> So if one creates a multi-segment transaction, then he/she should keep 
> the segments in order.
>
> Thanks.
>
What about adding following requirement to the spec ?

"A driver MUST keep the requests in order if a multi-segment transaction 
is going to be sent."
"A device MUST guarantee the requests being handled in order if a 
multi-segment transaction is received."

Thanks.


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