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From:   Arnd Bergmann <arnd@arndb.de>
Date:   Mon, 1 Mar 2021 16:19:00 +0100
Message-ID: <CAK8P3a1ZXbodV07TTErnQunCLWOBnzRiVdLCxBD743fn-6FbXg@mail.gmail.com>
Subject: Re: [PATCH v5] i2c: virtio: add a virtio i2c frontend driver
To:     Jie Deng <jie.deng@intel.com>
Cc:     Linux I2C <linux-i2c@vger.kernel.org>,
        virtualization@lists.linux-foundation.org,
        "linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
        "Michael S. Tsirkin" <mst@redhat.com>,
        Wolfram Sang <wsa@kernel.org>,
        Jason Wang <jasowang@redhat.com>,
        Wolfram Sang <wsa+renesas@sang-engineering.com>,
        Andy Shevchenko <andriy.shevchenko@linux.intel.com>,
        conghui.chen@intel.com, kblaiech@mellanox.com,
        jarkko.nikula@linux.intel.com,
        Sergey Semin <Sergey.Semin@baikalelectronics.ru>,
        Mike Rapoport <rppt@kernel.org>, loic.poulain@linaro.org,
        Tali Perry <tali.perry1@gmail.com>,
        =?UTF-8?Q?Uwe_Kleine=2DK=C3=B6nig?= 
        <u.kleine-koenig@pengutronix.de>,
        Bjorn Andersson <bjorn.andersson@linaro.org>,
        yu1.wang@intel.com, shuo.a.liu@intel.com,
        Viresh Kumar <viresh.kumar@linaro.org>
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On Mon, Mar 1, 2021 at 7:41 AM Jie Deng <jie.deng@intel.com> wrote:

> --- /dev/null
> +++ b/include/uapi/linux/virtio_i2c.h
> @@ -0,0 +1,56 @@
> +/* SPDX-License-Identifier: GPL-2.0-or-later WITH Linux-syscall-note */
> +/*
> + * Definitions for virtio I2C Adpter
> + *
> + * Copyright (c) 2021 Intel Corporation. All rights reserved.
> + */
> +
> +#ifndef _UAPI_LINUX_VIRTIO_I2C_H
> +#define _UAPI_LINUX_VIRTIO_I2C_H

Why is this a uapi header? Can't this all be moved into the driver
itself?

> +/**
> + * struct virtio_i2c_req - the virtio I2C request structure
> + * @out_hdr: the OUT header of the virtio I2C message
> + * @write_buf: contains one I2C segment being written to the device
> + * @read_buf: contains one I2C segment being read from the device
> + * @in_hdr: the IN header of the virtio I2C message
> + */
> +struct virtio_i2c_req {
> +       struct virtio_i2c_out_hdr out_hdr;
> +       u8 *write_buf;
> +       u8 *read_buf;
> +       struct virtio_i2c_in_hdr in_hdr;
> +};

In particular, this structure looks like it is only ever usable between
the transfer functions in the driver itself, it is shared with neither
user space nor the virtio host side.

       Arnd