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References: <5d3d8a27893734be954ebbe560f638fbafb3429c.1603778046.git.jie.deng@intel.com>
 <f0a25b9d-c1e7-21e8-0944-9fa5796adfca@redhat.com>
From: Jie Deng <jie.deng@intel.com>
Message-ID: <a1497eb0-91c0-551f-37e2-041b91c68e4b@intel.com>
Date: Wed, 4 Nov 2020 16:05:50 +0800
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In-Reply-To: <f0a25b9d-c1e7-21e8-0944-9fa5796adfca@redhat.com>
Subject: Re: [virtio-comment] [PATCH v3] virtio-i2c: add the device
 specification
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To: Paolo Bonzini <pbonzini@redhat.com>, "Michael S. Tsirkin" <mst@redhat.com>, Cornelia Huck <cohuck@redhat.com>
Cc: virtio-comment@lists.oasis-open.org, virtio-dev@lists.oasis-open.org
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On 2020/10/29 4:10, Paolo Bonzini wrote:
> On 27/10/20 07:00, Jie Deng wrote:
>> +The driver queues requests to the virtqueue, 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}
> Hi,
>
> one extremely common two-segment I2C transaction is not reproducible
> with virtio-i2c.  This is when a write is followed by a read: the master
> starts off the transmission with a write, then sends a second START,
> then continues with a read from the same address.
>
> Would it make sense to define the request like
>
> struct virtio_i2c_req {
> 	le16 addr;
> 	le16 written;
> 	le16 read;
> 	u8 bufwrite[];
> 	u8 status;
> 	u8 bufread[];
> };
>
> instead?
>
> Thanks,
>
> Paolo

Hi,

Do you have any comments on Paolo's proposal ?

Thanks.


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