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

[Arnd Bergmann]

On Tue, Mar 2, 2021 at 10:51 AM Stefan Hajnoczi <stefanha@xxxxxxxxxx> wrote:
> On Tue, Mar 02, 2021 at 10:42:06AM +0800, Jie Deng wrote:
> > > > +/*
> > > > + * 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?
>
> Linux VIRTIO drivers provide a uapi header with structs and constants
> that describe the device interface. This allows other software like
> QEMU, other operating systems, etc to reuse these headers instead of
> redefining everything.
>
> These files should contain:
> 1. Device-specific feature bits (VIRTIO_<device>_F_<feature>)
> 2. VIRTIO Configuration Space layout (struct virtio_<device>_config)
> 3. Virtqueue request layout (struct virtio_<device>_<req/resp>)
>
> For examples, see <linux/virtio_net.h> and <linux/virtio_blk.h>.

Ok, makes sense. So it's not strictly uapi but just helpful for
virtio applications to reference these. I suppose it is slightly harder
when building qemu on other operating systems though, how does
it get these headers on BSD or Windows?

       Arnd