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Subject: Re: [PATCH v16 5/6] vfio: ABI for mdev display dma-buf operation
From: Gerd Hoffmann <kraxel@redhat.com>
To: "Zhang, Tina" <tina.zhang@intel.com>,
        Alex Williamson <alex.williamson@redhat.com>
Cc: "Tian, Kevin" <kevin.tian@intel.com>,
        Daniel Vetter <daniel.vetter@ffwll.ch>,
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        "Lv, Zhiyuan" <zhiyuan.lv@intel.com>,
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        "intel-gvt-dev@lists.freedesktop.org" 
        <intel-gvt-dev@lists.freedesktop.org>,
        "Wang, Zhi A" <zhi.a.wang@intel.com>
Date: Mon, 06 Nov 2017 10:05:34 +0100
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  Hi,

> > I thought we had agreed to make this behave similar to
> > VFIO_GROUP_GET_DEVICE_FD, the ioctl would take a __u32 dmabuf_id
> > and
> > return the file descriptor as the ioctl return value.  Thanks,
> 
> If we follow VFIO_GROUP_GET_DEVICE_FD, we would lose flags
> functionality.
> Zhi and Zhenyu, how do you think about it?

The ioctl is simple enough that not having flags should not be a
problem I think.

Also note that dmabuf_id is received using the PLANE_INFO ioctl, so
should the need arise to negotiate something in the future chances are
high that it can be done using the PLANE_INFO ioctl flags.

cheers,
  Gerd