RE: [PATCH v10] vfio: ABI for mdev display dma-buf operation

[Zhang, Tina]

> -----Original Message-----
> From: intel-gvt-dev [mailto:intel-gvt-dev-bounces@xxxxxxxxxxxxxxxxxxxxx] On
> Behalf Of Kirti Wankhede
> Sent: Wednesday, July 12, 2017 8:45 PM
> To: Zhang, Tina <tina.zhang@xxxxxxxxx>; Gerd Hoffmann
> <kraxel@xxxxxxxxxx>; Tian, Kevin <kevin.tian@xxxxxxxxx>; linux-
> kernel@xxxxxxxxxxxxxxx; intel-gfx@xxxxxxxxxxxxxxxxxxxxx;
> alex.williamson@xxxxxxxxxx; zhenyuw@xxxxxxxxxxxxxxx; chris@chris-
> wilson.co.uk; Lv, Zhiyuan <zhiyuan.lv@xxxxxxxxx>; intel-gvt-
> dev@xxxxxxxxxxxxxxxxxxxxx; Wang, Zhi A <zhi.a.wang@xxxxxxxxx>
> Subject: Re: [PATCH v10] vfio: ABI for mdev display dma-buf operation
> 
> 
> 
> On 7/12/2017 1:10 PM, Daniel Vetter wrote:
> > On Wed, Jul 12, 2017 at 02:31:40AM +0000, Zhang, Tina wrote:
> >>
> >>
> >>> -----Original Message-----
> >>> From: intel-gvt-dev
> >>> [mailto:intel-gvt-dev-bounces@xxxxxxxxxxxxxxxxxxxxx] On Behalf Of
> >>> Daniel Vetter
> >>> Sent: Tuesday, July 11, 2017 5:13 PM
> >>> To: Gerd Hoffmann <kraxel@xxxxxxxxxx>
> >>> Cc: Tian, Kevin <kevin.tian@xxxxxxxxx>;
> >>> linux-kernel@xxxxxxxxxxxxxxx; intel- gfx@xxxxxxxxxxxxxxxxxxxxx;
> >>> alex.williamson@xxxxxxxxxx; zhenyuw@xxxxxxxxxxxxxxx;
> >>> chris@xxxxxxxxxxxxxxxxxx; Kirti Wankhede <kwankhede@xxxxxxxxxx>; Lv,
> >>> Zhiyuan <zhiyuan.lv@xxxxxxxxx>; daniel@xxxxxxxx; Zhang, Tina
> >>> <tina.zhang@xxxxxxxxx>; intel-gvt- dev@xxxxxxxxxxxxxxxxxxxxx; Wang,
> >>> Zhi A <zhi.a.wang@xxxxxxxxx>
> >>> Subject: Re: [PATCH v10] vfio: ABI for mdev display dma-buf
> >>> operation
> >>>
> >>> On Tue, Jul 11, 2017 at 08:14:08AM +0200, Gerd Hoffmann wrote:
> >>>>   Hi,
> >>>>
> >>>>>> +struct vfio_device_query_gfx_plane {
> >>>>>> +	__u32 argsz;
> >>>>>> +	__u32 flags;
> >>>>>> +	struct vfio_device_gfx_plane_info plane_info;
> >>>>>> +	__u32 plane_type;
> >>>>>> +	__s32 fd; /* dma-buf fd */
> >>>>>> +	__u32 plane_id;
> >>>>>> +};
> >>>>>> +
> >>>>>
> >>>>> It would be better to have comment here about what are expected
> >>>>> values for plane_type and plane_id.
> >>>>
> >>>> plane_type is DRM_PLANE_TYPE_*.
> >>>>
> >>>> yes, a comment saying so would be good, same for drm_format which
> >>>> is DRM_FORMAT_*.  While looking at these two: renaming plane_type
> >>>> to drm_plane_type (for consistency) is probably a good idea too.
> >>>>
> >>>> plane_id needs a specification.
> >>>
> >>> Why do you need plane_type? With universal planes the plane_id along
> >>> is sufficient to identify a plane on a given drm device instance. I'd just
> remove it.
> >>> -Daniel
> >> The plane_type here, is to ask the mdev vendor driver to return the
> information according to the value in field plane_type. So, it's a input field.
> >> The values in plane_type field is the same of drm_plane_type. And yes, it's
> better to use drm_plane_type instead of plane_id.
> >
> > I have no idea what you mean here, I guess that just shows that
> > discussing an ioctl struct without solid definitions of what field
> > does what and why is not all that useful. What exactly it plane_id for then?
> >
> 
> plane type could be DRM_PLANE_TYPE_PRIMARY or
> DRM_PLANE_TYPE_CURSOR.
> 
> In case when VFIO region is used to provide surface to QEMU, plane_id would
> be region index, for example region 10 could be used for primary surface and
> region 11 could be used for cursor surface. So in that case, mdev vendor driver
> should return plane_type and its corresponding plane_id.
Thanks, Kirti, do you mean there will be multiple DRM_PLANE_TYPE_PRIMARY and multiple DRM_PLANE_TYPE_CURSOR planes existing in the same time and region usage needs to use plane_id to distinguish among them? Is it for the multiple output or that's the typical way of region usage? Thanks.

Tina

> 
> Thanks,
> Kirti
> 
> > This just confused me more ...
> > -Daniel
> >
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