Re: [PATCH v5] i2c: virtio: add a virtio i2c frontend driver

[Viresh Kumar]

On 01-03-21, 16:19, Arnd Bergmann wrote:
> On Mon, Mar 1, 2021 at 7:41 AM Jie Deng <jie.deng@xxxxxxxxx> 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.

Why is it so ? Won't you expect hypervisors or userspace apps to use
these ?

-- 
viresh