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Subject: Re: [PATCH] i2c: virtio: add a virtio i2c frontend driver
To:     Jason Wang <jasowang@redhat.com>, linux-i2c@vger.kernel.org,
        virtualization@lists.linux-foundation.org,
        linux-kernel@vger.kernel.org
Cc:     mst@redhat.com, wsa+renesas@sang-engineering.com, wsa@kernel.org,
        andriy.shevchenko@linux.intel.com, jarkko.nikula@linux.intel.com,
        jdelvare@suse.de, Sergey.Semin@baikalelectronics.ru,
        krzk@kernel.org, rppt@kernel.org, loic.poulain@linaro.org,
        tali.perry1@gmail.com, bjorn.andersson@linaro.org,
        shuo.a.liu@intel.com, conghui.chen@intel.com, yu1.wang@intel.com
References: <0efc2605c8c06b4b1bf68cbad5536c4a900dc019.1599110284.git.jie.deng@intel.com>
 <f3ab5d7d-cce5-b34c-5931-dd5d74f065e7@redhat.com>
From:   Jie Deng <jie.deng@intel.com>
Message-ID: <6517879c-15d4-6265-761c-626cba9c95d6@intel.com>
Date:   Thu, 3 Sep 2020 15:19:02 +0800
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On 2020/9/3 14:12, Jason Wang wrote:
>
> On 2020/9/3 下午1:34, Jie Deng wrote:
>> Add an I2C bus driver for virtio para-virtualization.
>>
>> The controller can be emulated by the backend driver in
>> any device model software by following the virtio protocol.
>>
>> This driver communicates with the backend driver through a
>> virtio I2C message structure which includes following parts:
>>
>> - Header: i2c_msg addr, flags, len.
>> - Data buffer: the pointer to the i2c msg data.
>> - Status: the processing result from the backend.
>>
>> People may implement different backend drivers to emulate
>> different controllers according to their needs. A backend
>> example can be found in the device model of the open source
>> project ACRN. For more information, please refer to
>> https://projectacrn.org.
>
>
> May I know the reason why don't you use i2c or virtio directly?
>
We don't want to add virtio drivers for every I2C devices in the guests.
This bus driver is designed to provide a way to flexibly expose the 
physical
I2C slave devices to the guest without adding or changing the drivers of 
the
I2C slave devices in the guest OS.


>
>>
>> The virtio device ID 34 is used for this I2C adpter since IDs
>> before 34 have been reserved by other virtio devices.
>
>
> Is there a link to the spec patch?
>
> Thanks
>
I haven't submitted the patch to reserve the ID in spec yet.
I write the ID here because I want to see your opinions first.

Thanks