linux-kernel - Re: [PATCH v16 5/6] vfio: ABI for mdev display dma-buf operation

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Message-ID: <1509959134.30277.6.camel@redhat.com>
Date:   Mon, 06 Nov 2017 10:05:34 +0100
From:   Gerd Hoffmann <kraxel@...hat.com>
To:     "Zhang, Tina" <tina.zhang@...el.com>,
        Alex Williamson <alex.williamson@...hat.com>
Cc:     "Tian, Kevin" <kevin.tian@...el.com>,
        Daniel Vetter <daniel.vetter@...ll.ch>,
        "intel-gfx@...ts.freedesktop.org" <intel-gfx@...ts.freedesktop.org>,
        "joonas.lahtinen@...ux.intel.com" <joonas.lahtinen@...ux.intel.com>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "zhenyuw@...ux.intel.com" <zhenyuw@...ux.intel.com>,
        "chris@...is-wilson.co.uk" <chris@...is-wilson.co.uk>,
        "kwankhede@...dia.com" <kwankhede@...dia.com>,
        "Lv, Zhiyuan" <zhiyuan.lv@...el.com>,
        "daniel@...ll.ch" <daniel@...ll.ch>,
        "intel-gvt-dev@...ts.freedesktop.org" 
        <intel-gvt-dev@...ts.freedesktop.org>,
        "Wang, Zhi A" <zhi.a.wang@...el.com>
Subject: Re: [PATCH v16 5/6] vfio: ABI for mdev display dma-buf operation

  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